On the subject of a potential battle against Amethyst, to me, although it feels unlikely, I think it wouldn't hurt to be prepared. After a bit of poking around, I think I've drawn a few conclusions about her possible team. We already know her ace is A-Ninetales, and I recount a source saying her favorite Pokemon is Sylveon. Additionally, if memory serves, during the starter egg quest, it's mentioned that Amethyst likes Popplio, so I believe she could have a Primarina. The fact that we receive an Absol belonging to her tells me she won't use only Fairy types, which makes sense. My theory is that her team is a mix of Fairy and Dark, though I could be wrong.