She was probably talking about Bott Flies. They're parasitic insects that live in the healthy flesh of the victim. I say they were Bott's because she had worked to get them out of an infected animal before.

And maggots are actually good for an open wound, they keep it clean. Atleast that's what I heard a Veterinarian say.

Depends on the species of maggot. The good ones only eat dead flesh, effectively cleaning the wound. The bad ones eat everything.

How do you tell the difference?

You wait..