Good vd. Evil Palmers
Just a thought. Lynch seems to be a fan of duality. Good vs. Evil is kinda the ultimate in that regards. We all know Leland goes evil when possessed by BOB. I'm thinking the girl is a young Sarah Palmer. I also think the bug thing is positive. Thus setting up good and evil Palmer. Maybe that's why Sarah goes basically she crazy, evil won. Just digesting this all.
It's interesting I don't think we know yet if the frog-roach is good or evil. You're probably right that it falls hard on one side or other of the dichotomy.
It appeared to be an egg from the experiment's vomit so the inkling is that it is evil.
Was it working with the hobo/woodcutters when their words knocked out the waitress, mechanic and teenage girl or just seizing the opportunity it saw or perhaps working against them? Is their more than one frog-roach on the loose? Why did we see the waitress and mechanic being knocked out as well? Where these any relation to the teenage girl?
Sarah Palmer has "abilities" but I don't think she's ever visited the lodges (I could be wrong!) whilst other people with "abilities" have.