Does the info in post 53 offer any relief for the lady?
The lady wasn’t sued or prosecuted. The Federal Fair Housing Act calls for mainly civil recourse, not criminal. So in that sens, the police can’t make her take down a sign, though she opens herself up to liability.
Private persons seem to be subject to FFHA according to the text of the law.
http://www.usdoj.gov/crt/housing/title8.php