Lad'ia - OMelli D.

"The body you're in now used to be mine." So begins a note, which finds Mifani Thomas, woke up in one of the parks of London and surrounded by corpses in latex gloves. The girl is horrified to realize that she has amnesia and the only way to restore memory - to follow their own instructions in the note.
Soon Mifani learns that she is Ladya, a high-ranking employee of the secret organization Shahi, which protects Britain from supernatural threats. Trying to find out which of the Shahs and why he betrayed her, Mifani will face a consciousness divided between four bodies; aristocrat, who knows how to penetrate into other people's dreams; secret training camp where they turn capable children into deadly killers, and... conspiracy on a global scale.
Daniel O'Malley's novel in 2019 was filmed the eponymous series with Emma Greenwell in the title role.