Its gonna tough to get a picture I can try though its not very big only about maybe the size of a grain of rice almost the same dimensions. Its not red or anything. I should note shes had some health problems lately working on clearing up a cold and she was bleeding from her bottom and it was never determined where the bleeding came from only that it was from her bottom. This growth may have something to do with that?
It sounds like an in-grown quill, but I'm not a vet, so I could be totally off. That being said, here's a link, including a picture, of a discussion about ingrown quills on HHC. It's probably easier to show you a picture than you to show us a picture.. especially if it's on her rear end. Poor baby. Can you tell if she's in pain or not?
I don't have access to my images right now, but is it a white, round bubble, on the edge of her anus? NeMali had this twice in her life time. I can't remember exactly why doc said they could be happening, but I believe he said they were glands that had become irritated and infected. Doc always drained them with a needle and gave her antibiotics to clear them up.