I have a 17 year old Siamese cat, Phoebe. She's a pretty small cat, picked up from a cat rescue as a kitten. All her life she's had problems with throwing up her food. I grew up with it, so I didn't think about it I suppose, she's supposed to be my mom's cat. Its been getting worse though, and now she's having pretty bad shedding problems, and looks like she's getting skinnier.

She's on Purina One for sensitive systems, and any other type of dry food we've tried just makes her problem worse. She gets treats occasionally (she begs for them) and I've been giving her a little smudge of butter at night when she begs. It seems like this is making her vomit less often, but I'm not sure if its bad for her.

Any tips on a diet that would help? I realize its a little late in her life and it should have been fixed earlier, but if there's something I can do now, I want to.