I notice Cocoa has a swollen area on her side tummy close to her hind leg. I post a thread about her soft poo couple days ago here: Is my hamster getting wet tail? Will this swollen lump indicate tumor of some sort?
Maybe you could post a picture so that we could see what you mean? I have had a hamster with an recurring abscess before. I treated it by putting coconut oil on it every day for around a week or so. This helped a lot. Though from the area you said it is this might have something to do with his/her scent glands. I scanned this website and it appears to have some helpful info on the subject: What You May Not Know About Hamster Scent Glands - Veterinary Practice News - March 2012
I am no expert though, I hope you find what you are looking for!
The only way to know for sure is to take her to the vet. Whatever is causing the lump, it will need to be treated. I hope you can get her checked out soon x