You could try using the crystals at the spring as well, just learned about that recently so I'm not sure if it'll work for the collar yet
not quite, since the collar doesn't show up in the 'status' tab in the menu, and that's what you use to get rid of transformations using crystals. as far as I can tell, the collar is only added by losing to the werewolf in the outskirts tile in A11, and the only way I've found to remove it is with class state corruptions (having your color get overridden by a monster's)