Having the FBI arrest half of them and hold them indefinitely is within his authority, he just has to argue they’re terrorists. He could say every member of congress who made statements defending the January 6 insurrection is a terrorist and send them to gitmo. He’s more likely to come after the squad though.
Just to clarify your second statement, gaslighting is when person A tries to convince person B that person B did not see/hear/experience something that person B did in fact see, hear, or experience.
In OP’s situation, their girlfriend might be gaslighting OP if she texted “I’m getting an Uber home, see you in a bit” and then got mad and insisted she had told OP to meet her at the door.
All that said, I will echo many others in this thread and say that just because it isn’t gaslighting doesn’t mean OP is in a healthy relationship. OP, please insist on relationship counseling at a minimum.