I understand where she is coming from although I don't agree with her
There are loads of threads on MN about women who have had a child, or children, gone back to work and are still doing all of the childcare and all of the housework whilst their other half's do nothing and then sulk when they don't get sex on demand with no effort to try to get their wife in the mood first
And there will inevitably be several posters who come along and tell her that if she doesn't have sex with him then he will get it elsewhere, it will be her own fault, she should just have sex even if she's not in the mood just to keep him happy
From that perspective, the perspective that if a man doesn't get sex often enough he will automatically go and find it elsewhere then (assuming he doesn't get caught) going to a prostitute is less likely to break up a marriage then having an affair
However I don't think having paid for easy to access sex is doing wives a favour because it feeds into the narrative that men should be able to get sex whenever they want it.
What would do wives a favour would be their husbands picking up some of the work and parenting. Being left to do all the work in a (for the woman) sexless marriage because you have no energy left to make an effort and your husband doesn't need to make an effort because all he has to do is pay for it is not a favour.
But the lazy husbands are the ones I blame, not the prostitutes.