Rudy got neutered yesterday and is now wearing a fetching collar. She isn't feeling too good after her operation and is very subdued for her. She has already got the collar off once but l got it back on. The problem is Mimi our other cat (and Rudy's Mum) is freaked out by Rudy, hissing at her and chasing her. We are not really sure how to handle this? Do we keep them apart or do we let them work it out between them? They normally get on so well, cuddling, washing each other etc.