Painting for long term smoker tenant

[Tony Murphy]

A long term inherited tenant who smokes has asked me to repaint her living room.  She’s paid her rent on time for 7yrs so I don’t mind doing it for her.  Since she’s still smoking and the paint will eventually stain again, do I need to scrub the walls clean before priming and painting? or would painting over the nicotine without cleaning it seal it in and create more work in the future when she moves out and i repaint again?