Try giving her a bath and gently using a toothbrush to see if you can remove the purple!
I agree with all Hufflepuff said!
It's probably not something to get stressed about!
My hedgie Jack has been going through this as well! (Acting the exact same way!)
There are a large number of possibilities of problems. It could be an abscess, missing teeth, a tumor, or even intestinal problems! If he is still drinking and being active, it's a good sign. I'd take him to the vet...
DEFINITELY something to go to a vet for ASAP! Look for any cuts around the area you found blood and keep a close eye on her until you can get her to a vet!
Jack and I are wishing you the best!