a female detective investigates a series of murders with a BIG plot twist (spoilers)

[matthew]

hello all, i am looking for a book for my gf. i know this may be a long shot but these are all the details i have. thank u in advance SPOILERS AHEAD


POV switches between a detective investigating several murders (thought it was kids getting killed? but unsure.) and a woman named Victoria, as well as an unknown woman. *THIS IS THE SPOILER* at the end, it is revealed that the detective has DID and has been committing the murders unknowingly(?)

The hardcover edition is black, and it was read semi-recently (within the last few years) but neither of us can remember the title and searches have been futile.

[Jamie]

Could this be "The Crow Girl" by Eric Axl Sund? . Involves a detective investigating a series of murdered children, another woman named Victoria, and multiple personalities.

Description: " Det. Supt. Jeanette Kihlberg, who’s soul-sick from 20 years supporting her artist husband and early-teen son as a Stockholm police officer, and her solid colleague, Jens Hurtig, investigate an apparent serial killing spree that leaves bodies of homeless boys, drugged and mutilated, across the city. Soon Jeanette becomes romantically involved with Sofia Zetterlund, a psychotherapist with her own dark secrets, including a succession of multiple personalities , headed by the mysterious Victoria Bergman, who becomes the central figure of this challenging multifaceted descent into the abyss of evil and madness. "

[Genesistrine]

Or Headhunter Reimagined by Michael Slade? (Originally called just Headhunter, this is a rewritten version.)