I'd wipe it off whenever I see it so it doesn't have a chance to cause irritation. If it's stuck on, you can clean it off during a footbath... fill the sink/tub so the water touches her belly/tail area, let it soak, and wipe off.
I'm also wondering how it gets stuck there:
Does she have messy unformed poops that have a chance to stick to her rather than just falling away from her body?
Is she a big hedgie where poop is getting stuck in her skin folds?
A silly hedgie who likes to do things like poop against the wall and it gets stuck to her that way?
A young hedgie who ends up sleeping and pooping in the same place?
Depending on the cause, there may be ways of preventing it from recurring.