Would it be wrong of me to tell me gf not to post certain things?
Are you cutting her out of your life if she continues to post things?
I might if she doesn't stop.
It is okay to have boundaries in your life and to let your partner know what they are. If there is something that could hurt you, you should let them know, and they should consider that before doing things that could hurt you.
I'm big and bad, I'll just ignore every word she says.
It doesn't matter how big and bad you are, if you ignore her feelings too much then she might leave you. Is this worth having that happen?