She was taking on way more labor than her husband while working a full-time job. He still lashed out at her.

It’s totally up to you and your partner how you split the labor. There is no cut-and-dry way to do it that will make everyone happy. And it doesn’t have to make anyone happy besides the two of you. It doesn’t matter if your family approves of it, your friends think it’s weird, or what strangers on the internet think. But it does have to make sense for both of you. If one of you isn’t happy with it, then there is a huge problem. 

But you can also get into a routine that doesn’t end up working for you, and you don’t realize it until one of you snaps. You’re trotting along doing your usual thing, not realizing that you’re unhappy. Then you say something you might later regret, and it all comes tumbling down. But you need those moments sometimes to give you an opportunity to zoom out and make some changes in your life.