Excercise your rights.Unless I’m missing something local to you—entirely possible—there is no reason to warn, write a letter etc. you should know the law better than a random woman who says “she knows her rights” that’s just blowing smoke.

I showed the house to a woman who is on the VASH voucher.  

I've seen too many situations where the ex comes back and seriously harms both the woman he was abusing along with whoever is there trying to help.She needs to insist that her sister get on out of there and leave with her now or be prepared to leave her behind and help from afar.