My sister is being mentally and emotionally abused by her ex-husband to a point that miss effecting her health and she wishes she was dead.

I would please like to know what laws are behind this and what support she can get to make him stop. They divorced 8 years ago on the grounds that he told everyone she cheated just because she was confiding in a friend and he recorded the conversation and also uses that and threatens to post the information on various websites. He also added information about her on cheaters/liars.com. Se really needs help she is already extremely depressed for years and now I am afraid she might be suicidal. They have joint custody of their son but she also has physical custody and he does not pay for any of his expenses and sometimes picks up child when it is not his visiting days. Please help what can we do. Where should we start. .