By not saying anything about his hygiene issues, she had already been enabling it. By laughing at the farting, she has been encouraging the situation to continue. You can't laugh at something, and then complain about it.

Encouragement doesn't need to be actively vocalised. Silence is encouragement. Not setting the bar higher is encouragement. Not complaining is encouragement. Not asserting your boundaries is encouragement. Not shaming him is encouragement. Having sex with him when he's clearly filthy is encouragement. Washing his shitty laundry is encouragement. Treating it like a joke is encouragement. Living with it is encouragement.

His personal hygiene is entirely his responsibility. But her responsibility is how she responds to it. Thus far, she has remained silent for almost a decade. She has not demanded change. She has not asserted her boundaries, needs or expectations. By remaining passive, she has encouraged his behaviour to continue.

I hope that clarifies.