She wants some advice for her Christian classmates
Question

                In the University where I am studying there is a considerable number of Christians, and it has reached a stage where some of them are proselytizing, even though they are in a Muslim country and living among the Muslims. 

One of them even carries the Gospel with her, and another book about “faith”, on which there is a picture of the Virgin Mary (peace be upon her), and she encourages the girls to read it. 

After that, from speaking to her I found out that she is active in the church, and she teaches the children there. Now I am confused about how to interact with her and others like her. Should I cut off ties with her and warn others about her, or should I try to debate with her about her beliefs? 

Please note that I tried – once – to find out about some of what she believes so that I could work out how to debate with her, but I found out that she is well aware of matters of debate. It is as if she was trained in what she had to say, and she was equipped with how to debate and interact with Muslims. I did not have enough knowledge to argue with her or debate with her.
Praise be to Allah.Firstly: 
We 
    appreciate your protective jealousy (gheerah) concerning the religion of 
    Allaah, may He be exalted, and for your interest in calling others to 
    Allaah, and we ask Allaah to guide us and you and to make us and you 
    steadfast. 
Secondly: 
We do not 
    advise you to debate with your Christian colleagues, because you stated that 
    they have specious arguments that you are not able to refute, and you said 
    that you are a beginner in seeking knowledge. This makes us repeat this 
    advice in your case and the case of those who are like you.  The principle 
    is that the permissibility of that is limited to situations in which the 
    interests served by doing it are greater than the negative results thereof, 
    or in situations where arguing is kept at a level of friendly debate rather 
    than fighting.  Fath al-Qadeer by al-Shawkaani, 1/527. 
The purpose 
    which you seek to achieve by debating with the People of the Book or other 
    types of people who associate others with Allaah, or people who follow whims 
    and desires or innovations, can only be achieved if it is undertaken by 
    those who are qualified for it, who have sufficient knowledge of their own 
    religion and the other religion to debate it, and who also follow the shar’i 
    etiquette that is prescribed for us in such matters. 
Shaykh 
    al-Islam Ibn Taymiyah (may Allaah have mercy on him) said: 
Because the 
    followers of the Prophets are people of knowledge and justice, when the 
    followers of Islam and the Sunnah speak with the kuffaar and followers of 
    bid’ah, they speak with knowledge and justice, not with speculation and 
    whims. Hence the Prophet  (peace and blessings of Allaah be upon him) 
    said: “Judges are of three types, two of whom will be in the Fire and one in 
    Paradise. A man who knows the truth and judges accordingly will be in 
    Paradise. A man who knows the truth and judges otherwise will be in the 
    Fire. And a man who judges among people on the basis of ignorance, will be 
    in the Fire.” Narrated by Abu Dawood and others [and classed as saheeh by 
    al-Albaani in Saheeh al-Jaami’]. If he is one of those who pass 
    judgment among people concerning their wealth, lives and honour, and he is 
    neither knowledgeable nor just, then he will be in Hell, so how about one 
    who judges concerning sects and religions, and the basic principles of 
    faith, knowledge of the divine and other fundamental pricnples, with no 
    knowledge or justice, like the followers of innovation and whims and 
    desires. 
Al-Jawaab 
    al-Saheeh li man baddala Deen al-maseeh, 
    1/107-108. 
Because of 
    what Shaykh al-Islam mentioned here about the etiquette of debate, Allaah 
    says (interpretation of the meaning): 
“And 
    argue not with the people of the Scripture (Jews and Christians), unless it 
    be in (a way) that is better (with good words and in good manner, inviting 
    them to Islamic Monotheism with His Verses), except with such of them as do 
    wrong; and say (to them): ‘We believe in that which has been revealed to us 
    and revealed to you; our Ilaah (God) and your Ilaah (God) is One (i.e. 
    Allaah), and to Him we have submitted (as Muslims)’”

    [al-‘Ankaboot 29:46]
Shaykh Ibn 
    Sa’di (may Allaah have mercy on him) said in his Tafseer: Here Allaah 
    is forbidding arguing with the People of the Book, if it is done with no 
    knowledge of argument or with no appropriate basis, and He says that we 
    should not argue with them except in a way that is better, with a good 
    attitude, kindness and gentle speech, calling to the truth and making it 
    attractive, and refuting falsehood and making it unattractive, in the most 
    effective manner. The purpose behind it should not simply be to debate and 
    argue, and loving to win, rather the purpose should be to demonstrate the 
    truth and guide people. End quote. Tafseer al-Sa’di 743. 
You should 
    also focus on seeking knowledge. Before a Muslim learns about what others 
    believe, he has to learn his own religion and its rulings. So look for 
    sisters who are seekers of knowledge and start to learn your religion with 
    them. You can also make use of tapes by the scholars of Ahl al-Sunnah who 
    promote the way of the righteous salaf, especially if there is no one 
    available who can teach you. 
Your primary 
    concern should be to learn that which will correct your belief and worship. 
    Study the meanings of the Book of Allaah and the Sunnah of His Prophet  
    (peace and blessings of Allaah be upon him). 
This is the 
    sound way with which you should begin. Forget about debating with Christians 
    and other followers of misguidance and leave that to those who are 
    specialized in that field, for they are more able to debate with them and 
    point out where they have gone wrong. There are still people in the Muslim 
    ummah who can do this duty – praise be to Allaah. 
If you think 
    that the Christian proselytizing is having some impact on your Muslim 
    sisters, then you must warn them against making friends with these kaafir 
    women or listening to them. You can also provide them with books and tapes 
    which explain true Islam, and warn against false sects and religions. 
We ask 
    Allaah to help you to do that which pleases Him, and to enable you to gain 
    beneficial knowledge and do righteous deeds. 
And Allaah 
    knows best.