Cat losing weight again!!!

My IBD kitty has been doing very well for the most part. She has only vomited once in the past few months, which is great for her. Her appetite seems normal. In fact, she seems to be eating a little more than usual. She is alert and playful. However, for some inexplicable reason, she has started losing weight again. I can see her bones protruding a little. The vet used to monitor her weight closely (a weigh-in every two weeks) a while ago when she was first diagnosed and started losing weight rapidly, but she saw no further need to monitor when she started maintaining her weight again. The vet always does blood work when she has her yearly vaccinations, and nothing abnormal has ever shown up. The last time she had blood work done was about six months ago, and everything was fine. I am going to schedule an appointment with the vet, but I am a bit baffled by the whole situation. Has anyone else had a cat that started losing weight with no other abnormal symptoms?

I think you're right to be baffled.  And definitely right in scheduling an appointment.  Eating a little more than usual and losing weight is definitely NOT normal, unless the foods she is now eating or lower in fat and calories than before. 

Be sure they check her for thyroid problems and diabetes.  Just to rule stuff out.