I'm not a mother, summied, but I can relate.
When my wife and I announced our engagement, to my parents, my mom said, "You can't marry her!" Oh wow! We have been married for almost 37 years, now, and I still hear about that.
Some Moms can be a little possesive, and they know just how defenseless their poor sons can be, when up against a wily, conniving, husband catcher. And, every girl falls into that category. :-))
Good luck with it. I'm sure that it will take a lot of patience and sweet talking to bring dear old mom around.
Live simply, love generously, care deeply, speak kindly.
Cowards are cruel, but the brave love mercy.
"The purpose of life is to contribute, in some way, to making things better" Robert F. Kennedy