I´m vegan since 2 months now and i still get my period. Nothing changed. I´m not a mom ( I´m 19 soooo…) but I heard about some vegan moms and their kids are healthy, so your mom has nothing to worry about.
I’ve been vegan for over three years and it hasn’t affected my cycle negatively at all. If anything, it’s helped make me more regular! And four months ago I delivered the most perfect twins ever ? There really isn’t any reason to fret.