What do I do about my girlfriend insisting that she wants to spend the weekend with her ex at a cabin in a different state?

She basically told me that if i trust her that i should be fine with her spending the weekend with her ex boyfriend. That I'm insecure, and expressing toxic masculinity if i dont let her go. That I'm controlling and sexist. and bla bla bla.

Updates
2 mo
Let me add this detail. she's going to be gone for 4 days. I asked her if i could come along, she told me that there wasn't enough room. When i asked her where she was going to sleep she said "What do you think". I asked if the place had a couch, she said no, just one bed. So the implication is that she's going to share the bed with him. Hard no to all of that.
Updates
1 mo
Minor update, She went to her ex's cabin. I changed the locks and moved her stuff out, And i blocked her. When she got back, she found her self homeless, and furious. Thanks everyone for the responses.
What do I do about my girlfriend insisting that she wants to spend the weekend with her ex at a cabin in a different state?
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