All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Holding one`s-self to account for previous positions is a form of obeying Allah and a sincere act of worship particularly if this is accompanied with blaming self for any act of negligence. A Muslim should call himself to account before he is called to account on the Day of Judgment for doing so is a sign of religiosity and morality.
As for engaging in conversation with a girl for long periods without any Sharia-approved necessity, it will definitely lead to prohibited attachment because Almighty Allah Says {What means}: "Tell the believing men to lower their gaze and be modest. That is purer for them. Lo! Allah is aware of what they do." {An-Nur, 30}. Since looking at women is prohibited, then this ruling includes chitchatting with them without an actual necessity.
You should have asked to marry her if you liked her morality and beauty, and not kept chitchatting with her and made her, intentionally or unintentionally, get attached to you. Allah the Almighty Says {What means}: "O ye who believe! Follow not the footsteps of the devil. Unto whomsoever followeth the footsteps of the devil, lo! he commandeth filthiness and wrong. Had it not been for the grace of Allah and His mercy unto you, not one of you would ever have grown pure. But Allah causeth whom He will to grow. And Allah is Hearer, Knower." {An-Nur, 21}.
Consequently, you have to make sincere repentance and ask Allah to forgive you for what happened, then seek to marry her by overcoming all barriers or put an end to any small talk, and apologize to her. This is the legal and moral obligation required of you and the way to cure her from being unlawfully attached to you. It goes without saying that severing connection with her will be hard at the beginning but will work out gradually. According to medical experts, six months are enough for arriving at psychological weaning. However, continuing talking to her under the excuse of not being capable of severing contact for good will further complicate the problem instead of solving it. And Allah the Almighty Knows Best.