After Mirania gives Warren the medicine, head downstairs and speak to Lisa. Before she returns home, she'd like you to bring her to Stargazers' Tower, a place she describes as being very special to her. If you continue to her off on her own, she thinks you're just being mean and pulls a mean look! Agree to her request to continue how the story goes.
Here, Lisa will show you her "lucky star". In Seek Mode, look top left to the goddess statue, then right to the blue star, and up to the twin stars. After the cutscene, speak to Lisa. You can either "talk to her", or "touch her" (trying to touch her more than once results in a comedic cutscene in which Zael falls off Stargazers' Tower). Talk to her to progress the storyline. After, Lisa leaves for home, and you return to the tavern, alone. Head to your room and speak to Dagran, who advises you to get some rest, as your next task begins tomorrow.