I'm going to leave and not tell my GF where I'm going.
Why would you do that? Did she do something to you?
Yes. I'm tired of constantly dealing with the fact that she is late all the time.
Don't hide from her. Confront her and tell her how you feel. Discussing things is important when you are in a relationship.
I think she's a nice person. I'll just stop talking to her so I don't upset her by confronting her.
I appreciate that you don't want to upset your partner by bringing up a difficult issue, but ceasing all communication will hurt her even more. She will be hurt and confused by the fact that you abandoned her. I know it will be difficult, but you need to talk with her about how you're feeling.