Low blood platelets , abdominal pain and bruising

I have a very dear friend who is showing all of these symptoms and has for about 5 months. She has had a number of blood tests done and the doctors cant seem to be able to find anything wrong with her except that her platelet count is low. Her abdominal pain/stomach aches last about 3 hours or so. She can go a few days feeling perfectly fine and then the stomach will kick in pretty bad. She wakes up in the morning with new bruises on her body for no apparent reason. I believe she may experience headaches as well. Anyone experience this problem or symptoms and may know the cause of it? She has pretty much given up going to the doctor cause it doesnt seem to be doing any good. Any info or help would be greatly appreciated.