She became Muslim but her family do not know and they want her to marry a non-Muslim
Question

                I embraced Islam about two or three years ago, Alhamdullilah. Actually, one guy in my university influenced me to Islam. We used to study together in the university. and we both started liking each other and we wanted to marry. since my parents are kafir, they disagreed at all with this relationship and his parents also disagreed with the relationship. Now, my parents don't know that I am muslim now, I follow it secretly. I want to marry this guy and follow islamic marriage life afterwards. I don't want to marry somebody from their caste (kafir!), and my parents wants me to go back home and marry somebody in their caste. Is it necessary for both of our parents to agree with our marriage. Can we marry each other without their knowlege or permission now and tell them later? I fear that they will die the day they hear that I am muslim too since they hate muslims. I don't know how to convince them. Do I have to convince them for the marriage or can I just go against their wish. Please tell me if there was any stories during sahaba's time and what was the solution. I relly need help.
Praise be to Allah.
    Firstly: 

    Before answering your question, we would like to congratulate 
    you for becoming Muslim. This is the final religion which Allaah has chosen 
    for all of mankind, and He sent the Prophet  (peace and blessings of 
    Allaah be upon him) to be a bringer of glad tidings and a warner to all 
    people. Many of those whom Allaah has guided have entered this religion 
    before you, and many have been deprived of it because of their stubbornness 
    and pride. So you should always be grateful to Allaah for having brought you 
    out of the darkness of kufr and ignorance into the light of Tawheed and 
    knowledge. You have to learn the rulings of Islam so that you will become 
    more convinced of your choice and so that Allaah may make your heart 
    steadfast in adhering to Islam. 

    Secondly: 

    The fact that you are new in Islam does not prevent us from 
    telling you that this religion brought important rulings by means of which 
    the Muslim can protect his religious commitment, mind, wealth, honour and 
    lineage. Hence there are things that are forbidden in order to protect these 
    things, and there are things that are enjoined for the same reason. There 
    are two things that have to do with your question: 

    In order to protect honour and lineage, Islam forbids mixing 
    between the sexes, and it forbids a man to be alone with a woman or to touch 
    her with his hand, let alone anything that is more serious than that, namely 
    the sin of zina (adultery or fornication). Hence we regard a woman as a 
    precious jewel which should not be treated as a cheap product – as is the 
    case in the kaafir nations and the fools among the Muslims who follow them – 
    in advertisements, newspapers and magazines. Women have an important role 
    which awaits them, that of wife and mother. 

    The second matter has to do with protecting a woman’s 
    religious commitment. Allaah has forbidden marriage of a Muslim woman to a 
    kaafir man. This is something that is proven in the Qur’aan and Sunnah and 
    by scholarly consensus. 

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said:  

    It is not permissible for a kaafir to marry a Muslim woman, 
    according to the texts and scholarly consensus. Allaah says (interpretation 
    of the meaning): 

    “O you who believe! When believing women come to you as 
    emigrants, examine them; Allaah knows best as to their Faith, then if you 
    ascertain that they are true believers send them not back to the 
    disbelievers. They are not lawful (wives) for the disbelievers nor are the 
    disbelievers lawful (husbands) for them”

    [al-Mumtahanah 60:10]
It is not permissible for 
    a Muslim woman to marry a kaafir, according to the texts and scholarly 
    consensus, as stated above, even if he is originally a kaafir and not an 
    apostate (from Islam). Hence if a kaafir man marries a Muslim woman, the 
    marriage is invalid and they must be separated. But if he becomes Muslim and 
    wants to marry her, that can only be done with a new marriage contract. End 
    quote. 

    Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen, 
    12/138-140 
Thirdly: 

    In order for the marriage contract to be valid, there must be 
    a wali (guardian) for the woman, but it is not permissible for a kaafir to 
    act as the wali of a Muslim woman, and there is no difference of scholarly 
    opinion on this point. 

    Ibn Qudaamah said: 
As for a kaafir, he 
    cannot be the wali of a Muslim woman under any circumstances, according to 
    the consensus of the scholars, including Maalik, al-Shaafa’i, Abu ‘Ubayd and 
    as-haab al-ra’y. Ibn al-Mundhir said: There is consensus on this point among 
    all those from whom we acquired knowledge. 

    Al-Mughni, 7/71 

    Even in a situation such as yours, there has to be a wali for 
    the purpose of marriage. If no one among your family is Muslim, then whoever 
    acts in the stead of the ruler should arrange your marriage for you, namely 
    the Muslim qaadi (judge) or mufti or Shaykh of an Islamic centre or imam of 
    a mosque. 

    You do not have to ask your father’s permission to get 
    married because he has no authority over you as a wali. Once the marriage 
    contract is done, it is permissible to keep the news from your parents, and 
    you do not have to inform them. 

    Fourthly: 

    Even if the wali is a Muslim, it is not permissible for him 
    to force his daughter to marry someone whom she does not like. Islam makes 
    the woman’s consent one of the essentials of the marriage contract, and the 
    contract is not valid if she objects. If it is proven that she objects then 
    the Muslim qaadi should give her the choice between continuing the contract 
    or annulling it. 

    Just as it is not permissible for both parents or one of them 
    to force his son to marry someone whom he does not like, so too Allaah has 
    not made the approval of the parents or one of them a condition of the son’s 
    marriage contract being valid. But the son should be kind to his parents if 
    he refuses to do what they want. He has to do his utmost to win their 
    approval of his marriage to the one he wants.  

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: 

    It is not permissible for a father to force his son to marry 
    a woman whom he does not like, whether that is because of some fault in her 
    religious commitment or a physical defect. How many people have regretted 
    forcing their children to marry women whom they do not want, saying, “You 
    will marry her because she is my brother’s daughter” or “because she is from 
    our tribe” and so on. The son is not obliged to accept, and it is not 
    permissible for the parents to force him. Similarly, if he wants to marry a 
    righteous woman but the father does not want him to, the son is not obliged 
    to obey him. If the son is pleased with a righteous wife and the father 
    says, “Do not marry her,” he has the right to marry her even if his father 
    objects, because the son is not obliged to obey his father in any matter in 
    which that will not harm the father but will benefit the son. If we say that 
    the son is obliged to obey his father in all things, even in matters where 
    there is benefit for the son and no harm for the father, then many negative 
    consequences would result from that. But in situations such as this, the son 
    should be diplomatic with his father, and be kind to him as much as he can 
    and try to convince him as much as he can. End quote 

    Fataawa al-Mar’ah al-Muslimah, 
    2/240, 241 

    Fifthly: 
You have to do as much as 
    you can to save your parents and bring them into Islam, so that they and you 
    will find happiness in this world and in the Hereafter. You can use many 
    ways to call them to Islam, such as sending them e-mails, for example, 
    without them knowing that the messages are coming from you. You could give 
    their address to some of those who are specialized in Islamic knowledge and 
    da’wah to undertake this mission on your behalf. You can also avail yourself 
    of the nearest Islamic centre to their home so that some daa’iyahs can visit 
    them and call them to Islam. You can also use the regular mail to send them 
    tapes and booklets that will tell them about the Islamic religion. 

    You know more about their situation than others. Perhaps if 
    you tell them that you have become Muslim, that may open the door for them 
    to enter Islam too. If that is the case, then tell them, but if you think 
    that this will not do any good, and that it may have a negative effect on 
    them or it might cause difficulties for you, then do not tell them. You can 
    delay that for a while until Allaah opens their hearts. Seek the help of 
    Allaah and turn to Him with du’aa’, sincerely asking Him to guide them. 

    We ask Allaah to make you steadfast in adhering to this 
    religion, and we ask Him to guide your parents to Islam. 

    And Allaah knows best.