My hamster is losing fur and has a small lump on her belly?

please help guys. my hamster is a syrian and is abouot 1 and half years old. she is the most friendly hamster, if a little lazy, she is happy to snuggle up and fall asleep on you. she is the best, but recently i have been having alot of exams so i havn't been getting her out as often. when i got her out the other day i noticed she had lost alot of fur on her back legs near her feet. today i as i picked her up i noticed she has also lost fur on her belly and a small lump near where her bum hole is. it is under 1cm across it but quite red. she is still her usual self if a little more unfriendly and doesn't liked to be touched on that area. i dont know if it is something that i have just not noticed before as there was fur there, but i dont know i am really worried about her. she is still eating and drinking the same, what should i do? what could it be? i could take her to the vets but it is really expensive and i dont want it to change her (my friend took her hamster there and it started biting her after) please help guys, i want to know what is wrong with her desperatley. sorry its so long but i would really appreciate your help :)