Identify this time travel (?) movie.

I have a foggy recollection of a book I enjoyed when I was younger. All I can recall is that a junkie prostitute gets accidentally caught up in the travels of a guy who is (I think) a time traveler, or possibly some kind of Dr. Who-ish dimensional jumper and as a the book goes on gets gradually more with-it and competent.

EDIT: I meant to say “book” in the title, not “movie.” Could someone fix it, if possible?

Mindkiller, by Spider Robinson?

If there’s memory control involved that’s it, but Robinson’s work has gone out under multiple titles, Lifehouse and Deathkiller might ring the bell if Mindkiller doesn’t. (Assumning that’s the work in question.)

I didn’t watch that book.