All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
What is important is the condition of this girl now; if she is righteous, then marry her. Abu Hurayrah narrated that the Prophet said, “A woman is married for four reasons: her wealth, her family lineage, her beauty, and her religion. So choose the religious one, and you will prosper.” [Al-Bukhari and Muslim]
Her past sins do not prevent you from marrying her; there is no person who does not commit mistakes or who is not neglectful about the rights of his Lord.
What is important is that one returns to his Lord and follows the bad deed with a good deed so that the past sins will be forgiven. Allah says (what means): {But whoever repents after his wrongdoing and reforms, indeed, Allah will turn to him in forgiveness. Indeed, Allah is Forgiving and Merciful.} [Quran 5:39]
Besides, Abu Hurayrah narrated that the Prophet said, “By the One in Whose Hand my soul is, were you not to commit sins, Allah would replace you with a people who would commit sins and then seek the forgiveness of Allah; and Allah would forgive them.” [Muslim]
Also, Anas narrated that the Prophet said, “Indeed all of the children of Adam commit sins, but the best of them are those who repent.” [At-Tirmithi]
However, it is not enough that you judge based on what appears to you of her condition; rather, you should ask the trustworthy people who know about her conduct, and if they say good things about her, then perform the Istikhaarah (guidance-seeking) prayer and ask Allah to guide you in this matter as He knows everything and He knows the consequences of things.
For more benefit on how to perform the Istikhaarah prayer and some of its rulings, please refer to fatwa 81434.
After this, we hope that Allah will facilitate things. It is said that the one who seeks Istikhaarah never loses, and the one who consults people never regrets.
If marriage is facilitated with her, then all the best, otherwise, cut every form of relationship with her in order to be safe from the devil and his temptation. Indeed, it is not permissible in Islam for a man to have an affectionate relationship with a non-Mahram (marriageable) woman. Please refer to fatwa 81356.
We also point out the prohibition of abortion without a valid excuse, especially if the soul has been breathed into the fetus, as this constitutes unjustly killing a soul that Allah has forbidden to kill; please refer to fatwa 128722.
Allah knows best.