She did deserve it. But he also stooped to her level. She started it, but both showed a complete lack of maturity, Both chose to destroy themselves and another person.
When you intentionally ruin someone, you deserved to be ruined back. An eye for an eye makes the whole world blind, but the eye-stabbing stops when someone's afraid of losing their other eye and being blind. You just have to be that person to make the other person fear it.
[key word intentionally]
I know that I've been in a similar situation to this, the other person failed to take into account that I'm much smarter than them and know all kinds of ways to massively ruin someone but in my case it wasn't a relationship like this one they were abusing a couple kids so I made very sure said kids were liberated from that situation. Its amazing what you can see when you happen to be on the roof of a thirty foot tall building doing repairs.
He didn't stoop down to her level, he just revealed who she really was. We don't know her side of the story obviously, but personally, from what I can see, she got what she rightfully deserved.
[key word intentionally]