I have a question…

One of my cousins on my father’s side is Jewish. She converted 45 years ago when she married a Jewish man, and they’ve raised their son and daughter as Jewish, including Bar and Bat Mitzvah. She keeps a kosher home still, even after her husband passed away, and was going to the synagogue regularly (before Covid). She keeps a mezuzah on her door. She recently told me that a kid (twenty-something) told her "well, you’re not really Jewish, and your kids aren’t really Jewish either. Their mother has to be Jewish, not just their father." My cousin told him, "My children were born to a Jewish mother." She was very offended. Once you convert, don’t you become part of the community ? 🤔