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 [b]really[/b] 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 [b]were[/b] born to a Jewish mother." She was very offended. Once you convert, don’t you become part of the community ? 🤔