How would you react to a friend taking a pet (that you gave to them) to be euthanized (See details)

A few years ago I volunteered with an animal rescue. Long story short (since that isn’t the point of this question), the rescue screwed me over and left me with a ton of sick cats. I took care of them, and found homes or an alternate shelter for all of them.
One was a small, long haired tabby kitten with a severe abscess on her back. She was nearly dead when I received her, and I spent months and months nursing her back to health. Since her recovery was longer than the other kittens – she was a cat by the time she was ready to go to a home.
My very good friend decided that she wanted a cat to keep her company, since she lives alone in an apartment. Fast forward a few years – she doesn’t want the cat anymore. She finds the cat “annoying.”
This friend has announced on her Facebook status tonight that she plans to drop the cat off at the pound tomorrow. Needless to say, I’m absolutely furious. I’m not even sure how to react. To be honest, I’m questioning my ability to even maintain a friendship after this. I saved this cat’s life, and she is throwing that life away just because she is annoyed. Am I overreacting?