Possible symptoms of Leukemia or Lupus?

My friend has small bruises on the middle of her back for no reason that appear often. She has very severe Celiac's disease, and she is 13 years old. She is very drowsy with no energy, and has nausea and vomits a lot lately. I don't know if this is related at all but her gums and the inside of her mouth bleed when she's not even eating or anything, just for no reason. She was looked at by a friends mom who is a doctor, and she suspects that this could be Leukemia. She also had a herniated disc in her back recently which is now pretty much fixed, but could that be the reason for her bruises? My friend has an appointment at the doctors office to have her spine looked at and get blood drawn and tested. She also loses weight without trying and has excessive sweating and random tiny reddish spots from her stomach all the way down her hip. She is only 93 pounds and is losing a lot of weight for some reason. Is this Leukemia??? What are some other symptoms of Leukemia? What else could this be? Thanks for reading and please answer with anything you know, even if its just a guess!