Here is my situation:

A few weeks ago, I got involved with a girl. Nothing serious at first. Just occasional casual kissing. Then one night we got closer, things were going well. No sex yet. She went on a trip with another guy who she has a history with for 4 days. I don't think she did anything with him. The day after she got home, I spent the night at her house and had sex with her. That night we talked about the guy; She said she was over him and that she liked and wanted to be with me. We continued our night. The next morning, we talked a little bit. She wouldn't agree to be my girl. A few hours after I got home, she texted me telling me that she wasn't fully over the guy she went on the trip yet. That was about a week ago, and I haven't talked to her since.

Ok, so she's totally playing around. For one, know that she had sex with the guy even though she may deny. If you like the girl, just tell to leave the other fucker or else to fuck off.. Nice and easy. IMO she's a bitch. Dude, do u really want to handle one!! Ur call..

You made a mistake by asking her to be your girlfriend. I've made this mistake before and it more or less ruined things with the girl. A relationship just needs to happen, not be discussed and agreed.