If an NPC is due to give you a required item, but you have no available slots, you go into the normal "meet with NPC" mode. If you have 1 or 0 empty slots and you meet with the demon girl, you can "I LOVE YOU", give her a worthless item, "I LOVE YOU" her again, get rid of another item... and repeat the process indefinitely... when you want to "escape" remember to have 3 free item slots, since there are 3 required items you must take before she departs.Found at http://www.softwarespecialties.com/wizfaq_wiz6.html.
Mike