Trying to read my girlfriend?

[Taylor]

So me and my current girlfriend, who I live with have had a choppy relationship and in the past she has flirted with guys over facebook, talked about sex with guys etc, but didn't cheat. That stuff that happened is in the past so we worked past it but there has been tension here and there because of it. About a year and a half ago we got into a big fight and she ended up storming out, drunk mind you, and went to some house party. She's told me that she's cheated on boyfriend's in the past so I initially thought the worst happened that night. I asked her for hours if she cheated on me but she stuck to her answer and said no. So last night me and her decided to do some cocaine, and I've noticed that when we do cocaine we like to talk about things we wouldn't sober, you admit to things easier too. I asked her about the party she went to and wanted to see of she would admit anything, her first response was I don't know. And now I dont know... Suggestions? Cause this is killing me