I think it would be wise for her to make an appointment with a GI specialist. While colon cancer is very rare in people under 40, it's not uncommon. Those symptoms can be a sign of things other than colon cancer such as IBS, Crohns, or ulcerative colitis. The bump on the abdomen definatly should be checked out. Keep us posted on how she's doing!
Im no Dr but she knows her body best and I would have to say keep pushing till u find out what is going on. The 2 big things I know about is Celiac's and Crohn's my mom has Celiac's and I go Monday to see if dr is right with thinking I have Crohn's. I have bouts of diarreha, weight loss and pain (my lower right side) and yes at her age it is when Crohn's is normal found age 20 to 30. Im almost 31 and Iam going to have a colonoscopy done and hope they can tell me something with that. good luck and keep me posted. look up both of these and see what u think.
nikki