Is it okay if I suddenly leave a phone call with my girlfriend and her friend?
Why would you hang up on your girlfriend and her friend?
I was annoyed by something she said and I think I should leave for a while
People get upset in conversations, but ending a phone call in progress with your gf with no warning is inconsiderate. Explain to her what annoyed you and work things out instead.
Nah fam, I'm going to blow her off.
I really think that abruptly hanging up on them would only cause more problems, because it's an immature thing to do. It would be better if you let your girlfriend know what's bothering you.