She was sleeping in my bed and getting to know me platonically and flirting with me more and more each day and after around 2-3 weeks we had sex but sometime between that and the first day she did it with my roommate. I know it happened because my roommates girlfriend told my best friend after being really drunk. When I asked my girlfriend about it she said no and she got upset and started texting the guy and didn't want me to see what she was saying and the next day after drinking she said she did it with my roommate but she hasn't been with anyone since we were official. And she asked if I wanted to take a break and I said yes and she asked if I wanted to break up with her and I didn't have a response to that. If I knew during the time before I would have never ended up in a relationship with her and I feel like I can't trust her since she lied to me about it. I feel bad because my roommates all knew and watched us get close slowly over time and my best friend told me about it.
What kinda bothers me most is that the same night she slept in bed with me she had sex with my roommate earlier in the day and she lied to me about it.