Is your sister doing drugs with him if so that explain why she doesn't want to leave the house she is hooked on drugs and doesn't want her b/f to hogging all the crack .

If it was me I would call the probation officer and ask them do they do a drug test if he says yes then I would say , he's doing crack .

Have your sister go into treatment and get cleaned , her days are numbers if she is on drugs . In my opinion I could not sit back and watch her die from drugs . That b/f is toxic to your sis and u and your mother , he's effecting the people who love your sister .