The husband was the guilty party in this case. But knowing some of this couple's past struggles, I can safely say she wasn't blameless in the dissolution of this marriage. Not that this fact excuses anything.
"The heart is deceitful above all things, and desperately sick; who can understand it?"
~ Jeremiah 17:9 (ESV)
Only when we see clearly the role our hearts play in sin can we understand the role our circumstances have in it. Our struggles and temptations often trigger sin, but they never cause it. The origin of sin is always our heart and it's sinful desires.
The actions of others, external pressures, even our biology, these have an impact on our behavior via our hearts. But we cannot blame our circumstances when we sin - Adam and Eve tried that unsuccessfully (see Genesis 3).
Adam tried blaming Eve, and blaming God who gave him Eve. Eve tried blaming the snake in the garden (aka - Satan). While God punished the snake, He also held both Eve and Adam responsible for their individual choices.
So selfish desires lie within our hearts. They lead to sin. And sin leads to death.
Death of a relationship. Death of a family. ...eventually physical death - unless we're in Christ and will be raised with Him.
That's why we can't always follow our heart, as the common advice goes. But we can always safely follow the Spirit.
I realize "always follow your heart" is appealing advice. I'd like to always follow my heart too. But if we want to follow our hearts, we must first make sure they are anchored in Christ, His Word, and His Spirit. Not in our hormones, or our wants, or the pleasurable feelings a private message on Facebook can bring.
And that anchoring is pretty much a daily thing. Sometimes, hourly.