5 year old Dwarf Hamster - loss of weight?

I got 2 sister dwarf hamsters about almost 6 years ago. Pudgemuffin died in October after a nasty case of glaucoma, but Sasha is still around. They were not housed together (so this isn't mourning) because my mother had Sasha at her house, and I had Pudge at mine. My mother moved and had to give Sasha away, so I took her in. I know for a fact my mother gave her things like pizza crust and crackers, and I only give her her food and mustard/dandelion greens, carrots, green/yellow peppers, cubers, a pinch of raw oatmeal oats, and occasional fruits (not more than once a week) like strawberries, gs, bananas or chopped apples. She used to pe VERY round and puffy, but she has lost A LOT of weight. I understand her losing weight because of the diet change.. but she has gotten VERY thin. She also has a small mole-like growth on her lower tummy area. It doesn't seem to bother her, and I would take her to a vet, but the vets around here are nitwits and don't know much about rodents. Plus if it is a tumour or something, I couldn't afford to get it removed. Im hoping the two are at least unrelated. any ideas? She is more than 5 1/2 years old, and runs a lot. Is it normal for her to be losing weight like this? Thanks =)