She has committed haraam actions with her fiancé
Question

I am a Muslim girl. I pray and I fear my Lord a great deal, but I have a problem. I know a person who came and proposed marriage to me. My father agrees but he always postpones the matter because of family reasons. We cannot be patient and the more time goes by, the more I find myself attached to him. He used to ask me to meet him often, and we have met more than once. We spoke together and kissed one another as if we were married, and even touched one another. I know that this is haraam and is wrong. Every time that happens I end up arguing with him and get angry with myself. I asked my Lord for forgiveness and I prayed Istikhaarah, asking whether this person is right for me or not. Every time I tell him that we should only meet in permissible ways, but then we make the same mistake. I want a solution. Please help me.
Praise be to Allah.Firstly: 
You say in your question that you regularly observe the five daily prayers and that you fear Allah a great deal. We hope that you will be fine, and we ask Allah to make you steadfast in faith and in doing righteous deeds, and to keep evil and corruption far away from you. 
Secondly: 
Islam has blocked all the ways that may lead to committing immoral actions. Allah says (interpretation of the meaning): 
“Come not near to Al-Fawaahish (shameful sins and illegal sexual intercourse) whether committed openly or secretly”
[al-An’aam 6:151]
“Coming near” implies doing something that may lead to those actions. Islam also warns against men mixing freely with women. The Prophet (peace and blessings of Allah be upon him) said: “Beware of entering upon women.” They said: O Messenger of Allah, what about the in-law? He said: “The in-law is death.” Agreed upon. 
“In-law” refers to the husband’s relatives, his brothers, uncles, cousins, etc. 
Islam also warns us against being alone with a non-mahram woman. The Prophet (peace and blessings of Allah be upon him) said: “No man is alone with a (non-mahram) woman but the Shaytaan is the third one present.” Narrated by Ahmad, al-Tirmidhi and al-Haakim; al-Albaani said: It is saheeh. Saheeh al-Jaami’, no. 2546. 
All of this is for the purpose of protecting people’s honour against committing immoral actions, and blocking all paths that may lead to the crime of zina (fornication, adultery). 
Thirdly: 
The fiancé is a “stranger” (non-mahram) to his fiancée until the marriage contract has been done. So your going out with this non-mahram man, kissing him, meeting him and the other things that you mention are all haraam. Fear Allah and refuse to meet him until the marriage contract has been done, and be frank with him about that. 
See also questions no. 2572 and 23432. 
Fourthly: 
If this person sees that you are determined and righteous, this will make him more keen to marry you, because he will see that you have a strong personality and that you do not give in to your emotions.  Who would not want his wife to have a strong personality and be keen to protect her honour? That will affect him and make him change his ways and become more righteous, and you will be the cause of that.  
Fifthly: 
Put your trust in Allah and make a lot of du’aa’, especially at the times when prayers are answered. Be patient and remind yourself of that which Allah has prepared for those who are patient, as He says (interpretation of the meaning): 
 
“Only those who are patient shall receive their reward in full, without reckoning”
[al-Zumar 39:10]
Sixthly: 
We remind you that Allah says (interpretation of the meaning): 
“O you who believe! Follow not the footsteps of Shaytaan (Satan). And whosoever follows the footsteps of Shaytaan (Satan), then, verily, he commands Al-Fahsha’ [i.e. to commit indecency (illegal sexual intercourse)], and Al-Munkar [disbelief and polytheism (i.e. to do evil and wicked deeds; and to speak or to do what is forbidden in Islam)]. And had it not been for the Grace of Allah and His Mercy on you, not one of you would ever have been pure from sins. But Allah purifies (guides to Islam) whom He wills, and Allah is All-Hearer, All-Knower”
[al-Noor 24:21]
The Shaytaan gradually calls people to falsehood; before a Muslim commits zina, the Shaytaan draws him towards it by his being alone with a woman, and speaking to her, then kissing her, then meeting her in haraam ways, then the great evil which is zina – we seek refuge with Allah. 
As the saying goes: A look, then a smile, then a greeting, then speaking, then an appointment, then a meeting. 
Seventhly: 
You should avoid blind trust in anyone. How many women and girls have said, “My fiancé is decent, he is not what people think”? Then they fell victim to their naïveté. So you should not think of him in a positive way, rather you should be extremely cautious and careful. 
Eighthly: 
You should think carefully about this husband and find out more about him, because he is going to be your life partner. Is he fit to be your life partner even though he has tried to do something haraam and persisted in that? 
Ninthly: 
Try to find out what obstacles and problems are making your father postpone this marriage, and talk to him about the matter. If you cannot address him directly, then you can bring in someone who has an influence over him, whether that is your mother or your brothers, or any person who has any status in your father’s eyes and can urge him to hasten to do the marriage contract and explain to him the danger of a woman being left without a husband, especially as she grows older, because the opportunity may not come again, and can remind him of the bad consequences if he is careless in this matter. 
Some guardians – may Allah guide them – exaggerate about family problems, even simple ones, and make them an obstacle to proceeding with matters such as marriage; others may suffer as a result but they do not care about that or pay attention to their responsibilities.  
And finally: 
We ask Allah to guide you to all that is good, and we ask Him to guide your fiancé and to make it easy for you to do that which pleases Him, for He is Able to do that. 
May Allah send blessings and peace upon our Prophet Muhammad and upon all his family and companions.