Denise temporarily lets Jeremiah Fisher live with her in The Summer I Turned Pretty season 3.
This happens in episode 10, “Last Year,” after Adam learns that Jeremiah lied about returning to college and cuts him off financially. Denise offers Jeremiah a temporary place to stay, giving him support while his relationship with Belly and his family situation are both unsettled.
The arrangement connects Jeremiah’s story with Denise and Steven’s professional storyline. Steven quits his job to work full-time on his startup with Denise, while Taylor and Steven later move in together. Jeremiah is also invited to Christmas dinner by Laurel, but he cannot bring himself to enter the beach house.
Denise is therefore more than a background character in the final episodes. Her practical support helps Jeremiah through the aftermath of the canceled wedding and the family conflict that follows.