About two years ago Taz began to lose weight, rapidly. I found an old thread I started in Jan of 07. Click here. It's a long drawn out thread, but the bottom line is my vet gave him a cortisone shot and that seemed to work. She gave him a 10 day one to try it out. Then he got a few more 30 day shots after that. And I had to feed him anything he would eat. That took a long time to find something that worked for him.
Well, now he is having another issue. But that's another thread. LOL

Anyway, I hope you can find something that will work for your Ditte, so you can have her for many more years. She's not an old cat at 11, my Taz is 13.