My girlfriend lied and is cheating on me?

[helpmeplease]

Well my girlfriend and I were going to go to a movie but she cancelled on me and then she said she couldn't go. I later found out she went to a haunted house with one of her friends instead. So she ditched me. So instead of staying at home like a loser, my friend and I went to another girls house to watch movies. There were two girls there and 4 boys. And to clearaify things were all just friends hanging out having a good time.Its not like anything happened. Well she later text me that night and asked what i was doing and i told her i was at the girls house and she got really mad. she started posting multiple tweets on twitter like "**** you"," I thought things would be different with you #seriously #anygoodguysoutthere", "just not happy", and "pissed off, your an ***". I didnt respond to any of these tweets and i know for a fact there about me. Who elses whould they be about?!? this morning i told her i was sorry for whatever i did and asked her why she got so upset and she said she wasn't upset so i said "you seemed pretty upset by your twitter posts", then she replied back with "That doesn't mean there about you".so if there not about me who are they about?!? So shes either cheating on me by the statement "I thought things would be different, ANY GOOD GUYS OUT THERE" or she just lied to me by telling me their not about me cause obviously they are. I dont know what to do and i would like some opinions. THANKS