I love kitties! My cat's name is Abby. She's 14 years old and I've had her since she was about 7 weeks old. She was spayed as well.
I agree with Spyder. It was best for her health. I had two other cats that were not fixed and they got pregnant twice. It was extremely hard on their bodies and they didn't live very long and all of the kittens of one of them died from some mysterious illness.
Mimi will be just fine and so much better off, and you'll have her a very long time. :)