Alissa technically has two quests. Freeloader, Hypnoaddiction but there is an extra scene after she becomes a playmate.
After freeloader, she becomes a playmate. But to progress to dating her, you must finish her 'recovery' event. To progress to hypnoaddiction you must encounter her once in the Succubus Tower dungeon while being bullied by Rinny. Then pass about four or five days and talking to Cassie will trigger the event.