I might've run into a bug with May's quest. I don't think the quest ever actually started for me. I'm at postgame, can't find anything in Petalburg Woods, and have May stuck at 5 hearts. Trying to give her a gift doesn't even bring up the menu for gifts (which do work for all the other characters). As such, I think I'm currently locked out of getting Braixen and starting Sonia's quest.