First off, don't drain or do anything to the mass without veterinary consultation... it's just a really bad idea, so many issues could arise where you wouldn't know what to do. You can't accurately diagnose what kind of mass she has. Even though your mom is a registered nurse that's very different from an exotics veterinarian.
I haven't experienced tumors in such young hamsters, they were all really old. My hamsters who had tumors were brought to the vet, the vet prescribed meds but it didn't really do anything. They died not too long after.
I don't really know what an exotics veterinarian can do for your hamster. They're so tiny, so treatment options such as removal and draining are risky. You would have to speak to an exotics veterinarian to know for sure.
Besides seeing a vet, my best advice for you would to closely monitor her mass, food and water intake, behavior, and overall health daily. Be sure she can easily get around and run in her wheel.
There really isn't a lot that you can do for your hamster without seeing a vet. If it's growing, becoming irritated, or there are signs of decline in overall health you have to see a vet.
Goodluck, I really hope she gets better.
EDIT:
These links might be useful:
(broken link removed) <- Abcesses
(broken link removed) <- Cancer and Tumors