David Bradley (Gareth Fizel) is Kate Beckinsale's (Lindy) godfather. Beckinsale has posted photographs on social media of them sharing family Christmases when she was younger.
The restaurant where Lindy and Justin meet at the beginning of the film is the same location on the Nu Boyana Studio back lot in Bulgaria that was Sylvester Stallone's bar in "The Expendables" franchise.
In the opening scenes of the film, Lindy Lewis is committed to King Edmunds Hospital, Chiswick, London, UK. Though the hospital is fictitious, the place where it is located is not. Chiswick, London is where Kate Beckinsale grew up.
Lindy is diagnosed with "Intermittent Explosive Disorder," which is a real term. The initials for this would be IED and is more commonly used as an abbreviation for Improvised Explosive Device, which is a type of bomb made and used by unofficial or unauthorized forces, which could be another way of explaining Lindy. The Woman with No Name even says that "Humans are the most powerful, undetectable weapon."
When Lindy is at the graveyard looking at the casket, the headstone next to it has the name "Sherryl Clark" on it, which is the name of producer Sherryl Clark.