What do you think?

Have you talked to your man/friend about this yet? Maybe he could talk to his mom about this behavior?

A bit late to reply to your question haha but maybe you're still reading it?
Ask your mother-in-law why she's so worried..
And tell her not to be overprotective and make it clear that you're a good parent and she shouldn't interfere, that's really annoying! Just say it! It's your child and you'll take good care of your child.. That she doubts you says enough about her... I think she's a terrible woman if I read your story.. Very disrespectful of her too!

How are things now?