...What does the woman deserve?
She deserves equality before the law, both in respect and protection and in punishment in violation. Any other application of the word is subjectively problematic. Her conduct has breached the contract with her husband. All sorts of remedies follow. She is no longer entitled to the marital estate. Out of Eden goes she, so to speak with commiserate penalties attaching, as noted prior.
What punishment is proportionate to the injustice she has committed against her husband and against the State?
She's going to lose her status and many of the privileges the state had set aside for her, as she should. I set out her part above and prior.
But she has not battered either the state of husband and she has killed no one.
On judging...
1. There is no question about the matter of fact.
There's almost always a question and every bald fact can have mitigation, context that changes its nature. Without an intervening authority you'll never get to that or past many an errant assumption.
You invite tragedy, even before the consideration of the penalty, which is tragic enough. But even if it didn't and even if the facts were clear and asserting somehow that a beating was in any real sense more than vengeance rooted in emotional pain on the part of the husband, was in some way actually just, you invite disproportionate punishment within your context.
Why? Because one wife may endure what another cannot. One husband may inflict what anther can or will not. Regardless of the outcome threshold the administration of this "justice" cannot be uniform and therefore cannot be proportionate.
...So according to Christianity, it's not true that "a woman's body is not her own, but is her husbands," huh? Is that what you are saying?
"Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh." One flesh, not one with flesh grafted onto him and have fun with that.
You'll tell me that a woman has a right to bodily integrity, and this precludes the possibility of her being beaten by her husband.
I tell you that she has the same right as her husband and that no one has the right to beat someone who isn't threatening their person or the person of another.