My guess, after his old circle killed him, for her sake, instead of feeling guilty, they probably decided to double down on their incentive and took that extreme to the source, and either 1) raped her, or 2) killed her and each other, 3) both 1 and 2, or 4) raped her, recorded it and spread it through social media ruining her reputation, pushing her to committed suicide. I think suicide because why else would she have black magic and not the MC is due to the suspected cause of death.
She seems vehemently against the idea of even being "friends" with men, so maybe she WAS trying to be friends with MC and crew, but her favoritism towards MC unintentionally fueled the crew's jealousy leading to the deaths of both her and MC.
For all we know, MC could've been transmigrated by a Goddess while Crusher chick was transmigrated by the Demon King or something.