Are you freakin' serious??? He's not bound by law to give her shit while she's shacked up and gettin' banged by an unemployed, dead beat loser. Let 'em starve!!! Or eat each other. Your friend should care less...
Get the over it!!! Ignore her completely as if she doesn't even exist until she gets the hell out or either you do. At this point, she's showing that she's a disrespectful bitch with this type of behavior.
Count your blessings that you'll be rid of this burden within a short three months.