How does she get her mother to stop nitpicking her new boyfriend?

“About 4 years ago I got out of an abusive ten-year relationship. Since then, I’ve met a sweet, incredible man who has supported me so much that I’m finally opening my own business!
Over the last year, my mother has found ways to nitpick even the simplest things about him. She complains that he’s ten years older than I am and that he’s already a father.
How do I get her to stop? I just wish to be happy, but since I live under her roof, I’m afraid to say anything.”