Private London by James Patterson and Mark Pearson, 364 pages.

Hannah Shapiro has witnessed her mother's death and was almost murdered herself.
Fearing for her life she is put in a witness protection -of-sorts and moved to London.
Her guardian is the head of Private's London office.  When kidnappings occur and Hannah becomes one the latest casualties will her guardian be able to save her in time? Or will she end up dead and mutilated like the others? 
Little Miss Curious