I am going to tell my gf that I kissed another people in my dream and I liked it.
Why would you tell her about that dream?
I mean, my dream consisted entirely of the person I liked, just kissing
You should just keep that to yourself. Why set yourself up for drama when there isn't one?
But if I tell her, I figured she might be mad at first, but after a while she would just shrug it off and continue being my gf.
Well there's just no point in telling her about this at all really. It doesn't help anything so you should just keep it to yourself.