All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The Prophet said: "Islam wipes out all the previous (misdeeds)?" [Muslim] Since this woman has become a Muslim, she is not going to be held accountable, Allaah willing, for her bad deeds before she embraced Islam. Indeed, the Mercy of Allaah is vast, as Allaah Says (what means): {And verily, I am indeed Forgiving to him who repents, believes (in My Oneness, and associates none in worship with Me) and does righteous good deeds, and then remains constant in doing them, (till his death).}[Quran 20:82]
Therefore, you are not sinful about her acts of disobedience before you married her, so you should not worry about this and you should not be preoccupied by this matter. Rather, you should try to put an end to the whispers of the devil who wants to spoil your life and make you sorrowful. Since this woman has repented and became righteous, then it is more appropriate to keep her as your wife and you should have the intention of protecting her chastity and Allaah will reward you for this intention. Indeed, you will be greatly rewarded by Allaah, Allaah willing.
Finally, we advise you to endeavour to protect her and her religion by teaching her the religious rulings, and oblige her to wear Hijab, to avoid mixing with marriageable men, and so forth.
As regards carrying out an abortion, then this is forbidden except in case of an absolute necessity, so she should not do so, and you should not let her do so.
For more benefit on the ruling about abortion, please refer to Fataawa 87467 and 89880.
Allaah Knows best.