She's strange.

My cats do something similar. They sit on the back of an armchair next to a window, reach out across the gap, and hang onto the curtain. They'll sit there, front paws hanging from the curtain, for hours.

I used to think they got their claws stuck, but no, as soon as I approach to "help", they get up and disentangle themselves.

Furry little bastards. It's their curtain now.