Is it okay/normal to say mean things to someone's face because they rejected you?

This may seem like bait, but I'm asking a genuine question. This happened to my girlfriend where she rejected her former best friend (in a nice way…

Normal? Yes, I suppose so. I see people post about it enough.

Okay? Definitely not. Rejection hurts, but it’s no excuse to lash out like a toddler who didn’t get their way.

Common*

It’s not normal, that would mean it’s OK. It is common though.

Colloquially, normal and common are synonyms.