TIFU: Went out with a girl who had a boyfriend (I did not know this at the time) had sex with her, now she wants to break up with him for me I dont know what to do...

Some background (M 24years) i was at a small party (25 man) of my best friend about 2 weeks ago. He has a girlfriend who i got to know over the years we are just semi friends if that makes sense i invite her to my parties she invites me to hers but thats basicly our entire text convo.

So i was at this party started talking to a girl named Sarah (not her real name). She was alone at the party she was a close friend of my best friends girlfriend. So nothing really happened at the party we just talked and we clicked REALLY WELL got her snapchat and number. (I am more of a presonality guy then a going for looks guy so i was very interrested in her)

So we started chatting and hit it off even more after a week orso I asked her if she wanted to get a drink sometime? She agreed so the next day in the afternoon we went out. REMEMBER at this point I havent asked if she is in a relationship neither has she mentioned anything to me that she is in one.

So the day arrives I ask her if she needs a pickup she says "no i have someone taking me there". So i go out with her make some smooth jokes she grabs my hand and stuff yeah yeah. So after drinking and having lunch for an hour and a half I had to go because I had a appointment for work. So we walk to the place where she would be picked up.

This is where the beginning of the fuck up happens and i should'v seen the signs. So we walk back she holds my hand and drags me into a side alleyway where we make out for about 5 mins. So some information the alleyway connects to the parking lot but it's at an angle so you can not look into the alleyway from the parking lot if that makes sense. So I tell her "I need to go shall I walk with u to ur lift?" Sarah: "No No No hurry to your car and go to work I had a great time with you (with a smile)" (My car is in another parking lot because I live on that side of the city)

Later she text me if i wanna do something later in the week i invite her over to my place for dinner and we had sex. After I ask her if she needs a ride home she tells me no someone is picking me up. I let her go and she tells me her lift is waiting around the corner we make out and she leaves. So me someone who hasn't had a girlfriend in 5 years tells my best friend about this.

I go over to his place to tell him this he grabs me by my arm and tells me no you know she has a boyfriend whos shes been with for 3 years. At this point my hearth rate starts raising and my friend can see my shock. So i explain everything to him show him the texts his girlfriend is with us because I dont know what to do he doesnt know and calls in his girlfriend who tells us Sarah recently has been talking to her about breaking up with her boyfriend of 3 years since a couple of days.

I am someone who would never EVER cheat on someone or with someone so I feel AWFULL AND HEARTHBROKEN. But this is not where it stops because I felt so much anger and guilt towards Sarah I walk outside of the room where my best friend and his girlfriend are and tell them i am calling her. They try to stop me I go outside and call her.

She picks up the phone and tells me wait let me get someone more privately so i know her boyfriend is there. I tell her everything she starts crying and blaming it on me that I never asked if she was in a relationship which is ridiculous after some time talking we calm down and talk about it, we are explaing stuff to eachother then, she tells me she wants to break up with her boyfriend and be with me. My hearth RAISES to the moon and i dont know what to do i tell her PLEASE SARAH DON'T and start yelling it over the phone. My friend and his girlfriend come in and see me hang up the phone.

So thats where i am now this happened today. I am Hearthbroken sad mad everything because I done something I could'v never done if she just told me she had a boyfriend. She texts me still I open them then make them unwritten again she tells me she is sorry and she really likes me and she doesnt know what to do and still ASKS ME IF SHE NEEDS TO BREAK UP HER BOYFRIEND. And i dont know what to do now.

After this my friend also told me it was probably her BOYFRIEND WHO DROPPED HER OF ON BOTH OF HER DATES WITH ME! because she doesnt have a driver license. Which also explained why she didnt want me to take her to the car.

TLDR: Clicked with a girl on a party went out with her, later that week asked her over to have dinner (didnt only have dinner). Also found out it was probably her boyfriend who dropped her off at both my place and the city where we went out. Now she wants to break up with her boyfriend for me. That is not how i moraly work so i am hearthbroken sad mad and ghosting her. I did not know or ask beforehand if she was in a relationship.