What Causes Nausea, Fatigue And Vaginal Rashes While Treating Worm Infestation?

my 18 year old granddaughter has been extremely tired, no energy, pale, and nauseated. She also has had this rash between her vagina and rectum for the last 4-5 mo. at least. She seen a Dr. about that and they had her on a yeast medicine for that. It went away only to come back so they put her on yeast medicine again with an Anti biotic too. But it has not gone away and then, Last night when having a bowel movement she had a worm about 5 long coming out of her rectum and she had to finish pulling it out. This sounds so gross I know but there is no other way to explain it to you. I am so very worried about her. She has had a history of gastric problems. We almost lost her once because her bowel was twisted and she ended up with emergency surgery to fix that. She has to eat gluten free because flour and things like that make her very sick. She also, not that this may or may not have anything to do with this problem, but she had surgery on her neck because she has Arnold Carrie. Please can you give me some idea what this might be?