I'm not going to let my girlfriend sleep over anymore.
Why not? She's your girlfriend.
She snores so loudly, and it's annoying the fuck out of me.
I understand being annoyed by her snoring, but that seems like a silly reason not to let her stay over anymore. If her snoring is that loudly, maybe she should see a doctor to see if there is an underlying issue.
I would rather just not let her sleep here anymore.
Spending time with your girlfriend is important and if you refuse to let her sleep over, she may feel hurt and want to end the relationship. Talk to her if her snoring is bothering you that much so you two can find a solution.