Why?
There are large numbers of both married women and single women who prefer Ms. And no, you don’t pronounce Ms. as Miss. It’s more of a z sound than an S sound. If you’re pronouncing them the same way, then that’s a significant chunk of your problem.
The reason it makes sense to pronounce Ms. as “mizz” is so that people can tell it apart from Miss!
“Missus”, however you pronounce the middle of it, has an entire extra syllable.
Everybody’s got an accent. Many people don’t recognize their own, because they define it to themselves as “normal”. But it’s no more normal than any other accent, including the ones they define to themselves as “strong”; and it’s bound to sound like a strong accent to anyone who’s used to a significantly different one.