Wow ursketching that couldn’t be too easy, but every MIL is different- there are many many MIL’s that have the same view as yours and look at their daughters and daughter in laws very differently I think mostly because they were extremely close to their sons and they feel the DIL grabbed him away but I’m sure there are loads of reasons….
But you should just know that there many many thousands in your boat! And I’m totally maskim that it’s hard in your case to call her Mom.
BTW now that you’ve made the leap- keep posting!!!