Even a "patriarchal" Troll society didn't stop Drub from becoming Queen. I think Maggoty is less a leader than she is a type of counsellor. I don't know if she would actually want to rule a Troll community as much as tell the leader what to do. She prides herself more in herbal medicine than in trying to run things. Maggoty picks on Picknose because she is the spawn of mother-in-law jokes.
You have to give the Trolls credit for all the healing they have to do without the benefit of magic.