LaBrava by Elmore Leonard (1983) Arbor House

An ex-Secret Service agent turned photographer lives in a building where the man who owns it, Maurice. is in his eighties and knows an ex-movie star.

LaBrava runs into the woman at a rehab check-in after she was arrested for throwing a beer bottle at a police officer.  Another man comes to see her, to ‘take her home’ and presents a security company badge trying to impersonate a police officer.  LaBrava puts him down until Maurice can get the star into his car and they leave.

The impersonator continues to come around and bother her, so Maurice gets her to come to his building and use one of the empty rooms.  LaBrava remembers her in movies he saw when he was 12.

But, of course, there is more to the story.  There is a murder plot to bilk her for $600G, which she does not have, but which Maurice will lend her so she can stay safe.