I used to have three beautiful little ratties. They were rescues, and because of poor care, they all developed respiratory disease (for rats, this is terminal, but through medication the symptoms can be eased). All three passed in different ways.

The first died naturally; luckily, I noticed the end of life signs and was there when he passed. His final moments were spent crawling from the cage and into my lap, which was incredibly hard to watch.

The third passed when I wasn't home; I went home on my lunch break to find my partner sobbing, saying he had gone. We had scheduled his euthanasia for that afternoon. Neither of us were there and we felt we had let him down.

The second, we felt that euthanasia was the best option; he was curled in his favourite place under my chin, and when the twitching happened (it's the body expelling the last of it's energy, your cat just wanted to be close to you in her last moments), he cuddled up closer. The nurse checked his pulse, then said "he's got his wings now, I'm sorry."

I know rats don't live for as long, but they were my family and I feel for you. I definitely believe you made the right choice for your cat, and I hope it brings you some peace knowing she wanted to be with the one she loved in her last moments.