She's allowed to have whatever opinion of whatever and whoever she wants. That does not make it true, or applicable, or anything. You do not have to give it more weight than your own perspective when making your decisions, or any, for that matter. You do not need her to agree with your decisions to make them the Right Decision for You.
When she's telling you she thinks you're doing something wrong, you can tell her you disagree. You can tell her you hope for her support but that it doesn't change your decision. You can tell her your husband has made his own bed, and you are done trying to keep him from lying in it. Or you can say nothing. What you don't have to do is convince her that she is wrong. Because you know you are right.