OP, i'm surprised this hasn't been mentioned already, but your sister needs to get all of her financial ducks in a row - copies of bank statements, his pay stubs or checks, tax returns, any investment and retirement accounts, etc. i can assure you, when she gets the papers from her husband, she WON'T be happy (i'm a former legal secretary and i've seen it many times). he's going to give her little or nothing, and she's going to need a SHARK of an attorney to make sure she gets an equitable settlement, not only for herself, but for her daughter's sake. nothing against legal aid, but your sister is going to need a private attorney-the legal aid lawyers do the best they can, but they're totally overwhelmed, at least, where i live.
she should also go to a doctor and have a complete physical, including a gynecological exam with full STD testing.
i'm sure there's more, but neck pain is preventing my brain from fully functioning right now; i'm sure someone will jump in and fill in the blanks for me.

to your sister and niece.