What is it about hair ties specifically that makes cats go nuts?? It’s so funny. I keep them away from my cat precisely because I’d heard stories like yours of kitties eating them and needing surgery, but if he manages to find one he goes crazy, and he’s always trying to get into the cabinet where the Tupperware full of hair ties lives.
If you need a safer alternative to hair ties for when she feels better, these have been a big hit in my house- Whisker City® Spring Toys Cat Toys - 4 Pack | cat Multi Pack | PetSmart they’re too big to eat but they don’t break like the plastic springs, and you can bend them into different shapes.