Have you taken her to a vet? She might have a thyroid issue that retains weight and might need medication or a specific diet.
Other things you can do, besides monitoring her food, are nosework games (hiding her dinner so she has to sniff it out) or puzzle toys. This one, this one, and this one can be used while lying down so she doesn’t even have to move too too much for it.
But vet first and foremost, if you haven’t already. Good luck! -C