Dear Passy, I thank you for asking this question here and seeking a Godly advice. Please what she wants is to make you get involved in FORNICATION which is a SIN.
If she really loves you, she will not ask you to compromise your principles which is in line with the Word of God and she'llwait since she knows that you'll definitely marry her. Remember that your body is the temple of the Holy Spirit which was bought at the cost of the BLOOD OF JESUS.
Explain these things to her, assure her of your love and re-affirm your devotion to her BUT tell her that you cannot sell your soul to the devil by engaging in the act of fornication with her in as much as you love her.
Also, let her know that sleeping together with one’s partner before marriage raises suspicions and distrust during marriage. Let me stop here for now.
Remain richly blessed..