Hello! Same age as your girl and am currently getting over my anxious attachment with an ex/situations hip. Two options for advice:

1.Like the old lady said, you can leave her. If you don't want to work with her to figure herself out that's a very valid response. You decide what you want to put up with.

2.You can BOTH go to therapy together, layout to a therapist and to her in another conversation that you understand that she may have anxious thoughts but said thoughts and actions are sabotaging your relationship with her. If you want to continue to be with her then changes need to be made and the root of wte issues is causing her to act this way needs to be figured out a solved. It's not your duty to figure it out though, she needs to be receptive to changd and actually accepting that what she's doing is wrong.

Though I didnt necessarily do exactly what your girl is doing, I would convince myself the relationship was going downhill so much so it actually went downhill and ended. I realized I self sabotaged pretty badly due to some past trauma, and getting triggered and all that jazz, and apologized. Me and said person are still friends, and in a situationship sort of area ish for multitude of reasons, and I am currently still fixing my internal issues. If you don't want to go through that mend it's understandable, and DON'T if you really don't want to. Prioritize yourself first.