Should I ask my girlfriend to leave a groupchat?
That sounds bad. Why are you going to ask her to leave the groupchat?
I'm planning to cut her off because she make me feel not important
Even if she sometimes makes you feel unimportant, you shouldn't tell your girlfriend what to do. Show your girlfriend respect and let her decide what she does and doesn't do.
She's mean to me. I am minding my own business and she comes in with her disgusting shit.
If the relationship is not going well, just end it. It would be better than trying to control her and tell her what to do.