I think if you can feel her spine then that can be a problem. Have you tried giving her canned pumpkin? Jake throws up a lot at certain times of the year but they shouldn't be losing that layer of muscle protecting their spine. I hope your cat doesn't go through that much of a weight loss this year. I noticed Jake barfs less if I'm giving him even a little canned food every 1-2 days (and/or pumpkin). Sorry it took me a while to respond. I've been a bit under the weather.
It also helps if I comb and brush him a lot during the time he's losing so much fur. BAthing him helps too. I can get a plastic grocery store bag full of fur during his molting season, when I bathe him and then comb and brush with a blow dryer. It's amazing. So I figure it's that much less fur for him to swallow!
Interesting that you mention canned pumpkin. I had heard that before, but the molt season starts in March, and I couldn't find canned pumpkin anywhere, so I substituted baby food squash! This really seemed to help, so I'm going to buy some again this year.
I can't imagine trying to bathe Dusty, and no way would she put up with a blow dryer!. I think I'd be torn to ribbons. She is such a scaredy cat.