I could get behind that, certainly. If the artwork you're supplying for inspiration is of any indication, the lady would seem unnaturally young to the townspeople. Maybe she's an outlander noble or a widowed duchess or such, and the local authorities have always been a bit skeptical, critical, jealous..? They escalated from levying taxes and unfair citations to actually taking her into custody on trumped-up charges (upon which no one can really agree... ranging from 'treason' to 'consorting with demons').
About dynamics... perhaps the adventurers are just a few sparse years apart in age, and would have arrived and left on slightly different schedules, but they do know each other well and have only been separated for a few years. I like your suggestion that no one really knows how she manages to end up being their mentor... maybe it was luck, or maybe she called them somehow. But regardless of their doubts, they're still loyal enough to return to help her.
I'll be honest in the hopes this works out... aside from underage sexual activity in the story, which I won't want included, I would open up other elements of sexuality here, ranging from Babysitter's Club crushes to secret practices of orgiastic rituals. It would make sense for romantic feelings or curiosities when tutors were in their late stages of training (late teens).
We can work on their younger background as we go along, too, perhaps? Like, "well, I'm seeing my character has some rivalry with X, so how about we tell a story about how we used to be super-competitive as teenagers..."