Seems like maybe MIL never expected your relationship to last.

Mine was like this with everything we did. First it was we'll never marry, then it was it won't last, we'll never be able to save enough money to buy a house, our kids won't make it through school or college, we'll never sell our house and move out of state far away from her. If it were up to her, we wouldn't have gotten married, bought a home, educated kids, and a dream home in the mountains. You'd think she'd have learned that whatever she ways we can't do, we do.

Live your lives how you two decide to and leave her out of it.