There's a good chance that when Reze died to Makima in the ambush, she thought Denji called her to the cafe as a setup for her to be killed by Makima. Considering Denji's speech during their battle about him still having Makima and how he should've never kissed Reze ("Oh, Denji, you're that witch's pet?"). This would also be the most plausible reason she never returned after Makima's brainwashing wore off.