If she represents any threat to him and/or his daughter, you should first report it to the police.
Magic is only used as a last resource, when all the other options are run out. If she beats him than that's domestic violence. If you have no proof of that, just report it and say that you suspect such thing is happening ( if you don't feel comfortable them knowing who told the police, you can make it annonimous ).
Magic can't solve everything. Report it to the authorities.