This is really awful for you, and I am so sorry you have to go through all this worry and stress on top of loosing this precious furbaby.

I think it is all about GREED now with this woman, she is left with large vet bills and no cat, so she wants to blame some-one and obviously get out of paying and you my dear are her scapegoat.

Surely no court in the land would rule in her favour, You did everything possible for this furbaby, don't feel bad about that, hopefully she will re-consider her actions and not go ahead, I hope for that resolution and soon, HUGS to you at this really uncomfortable and worrying time.