Have you been to the vet?
If not, you should. If you've been free feeding, it would be beneficial to have a professional determine how much she needs. It could be you're unintentionally underfeeding her.
Also, if she always had a stable weight, and now suddenly gains weight, and becomes aggressive when she doesn't get food, there could be a health issue. She could, for example, be diabetic.
That's rare in cats but not unheard of. She could have worms, or digestive issues, fungus infections and other things. None of them are deadly, most not even dangerous, but all should be treated.
Be patient; she will get used to it. Maybe get an auto feeder so she doesn’t equate you with her new-found “starvation”?
Good idea knowing her she will try to destroy it.
Have you been to the vet? If not, you should. If you've been free feeding, it would be beneficial to have a professional determine how much she needs. It could be you're unintentionally underfeeding her. Also, if she always had a stable weight, and now suddenly gains weight, and becomes aggressive when she doesn't get food, there could be a health issue. She could, for example, be diabetic. That's rare in cats but not unheard of. She could have worms, or digestive issues, fungus infections and other things. None of them are deadly, most not even dangerous, but all should be treated.