So this game was kinda okay-ish RTP game for me. I did beat the game wondering if I did fight all the bosses, including the secret one, and wondered if it's that treasure chest. Also not sure what the different between giving her the cure or not is; in the end you still fight her before she drops the item. I want to point out that even if you didn't fight the treasure chest boss, when you are about to fight the Chimera Reflection, the character dialogues will still mention being attacked twice in a day. I'm currently sort of doing a second playthrough just to recheck if I did fight all bosses or not; so battles were quite plain and long for me to not be so sure if I did or not. So there is the Yeti, Grave Attendent (treasure chest), Mary's Reflection, Chimera Reflection, and then the two rounds for the last boss... I think may have fought everything.