So my girlfriend keeps saying she will hangout with me as soon as she can she's been busy which is definitely understandable but she's been really distant lately and the other day I got her a pack of cigarettes because she didn't have the money for them and she said she had errands to run and didn't mention hanging out with anyone at all and that we could only hangout till 7 and she was trying her hardest to come asap to spend as much time as possible together so anyways she takes hours and finally at like 5 she says she's on her way and she gets there at like 5:15 and says "does it smell like fire in here? Michael was lighting shit on fire" then acts like she slipped up and didn't mean to say it and instantly shuts up my question is do you guys think she's cheating if not do I have a right to be mad that she has time to hangout with her friend who's a guy and not me?

Confront her and ask bluntly, no emotion or anything. And if you know the guy shes talking about you can always ask him or get someone to do it for you.
In my opinion it certainly does seem like she is.

Just ask about it, tell her how you feel, and keep an eye on it.

It may just be that she has guy friends who aren't you and, assuming you'd freak out about it (which you apparently are already), opted to hide it from you to avoid the drama. But she needs to explain that now that she's slipped up.

Honestly, I don't know. Just wait to find out. Might hire someone to find out. someone might know.

It does depend on how she reacts to him telling her that though. You know her better than any of us so the first suggestion of telling her straight up should only be done if you know she wont reacts by talking about "suspicions" or something.