###Here comes the Spoilers###
-So to get into the cave, you'll need pickaxe which can obtain by trading with a NPC in one of the buildings on the east
-Then, in order not to be affected by her spell, you'll need a talisman, this can be obtained by playing the organ and impress Joan the priestess, and the tutorial can be purchased in Elisa's shop.
-Then, once you interacted with the wanted on the wall of the jail, or you have already bought the house for sale, you'll get to option to decide if you want to put her in the jail or invite her to your house as a new shelter.
The quest line wasn't really clear enough though, I admit that :P