We have also at this point asked the day care worker and she has argeed to place her in a diffrent area than the other children at lunch. She no longer is doing it! She is also eating better and not tring to be the class clown.
My little cousin also did this for awhile when he was 2. He would pretend he was sick, grab his stomach and let everyone know he had to vomit, then he would run to the bathroom and make himself throw up. It wasn't until we started ignoring him that he quit. Once he realized we weren't going to pay attention to him he got bored and quit doing it. It's just a weird stage he went through, but he's almost 4 now and hasn't done it since. Good luck!
Re: the potty training, take it in stride and be patient. If you display impatience or emotional upset, it will only complicate the toilet training process.
Re: the self-induced vomiting, tell her this behavior is not acceptable and that, whenever it occurs, she will be in time out. Should she do it, place her in time out immediately. A five-minute time out, sitting quietly in an adult-size chair, is suitable. Use a timer to track the time, and start the timer only when she is seated and quiet.