Future Mother-in-law says I wasn't raised correctly. Who is she to judge me?

My FMIL apparently asked my FH about my family and upbringing. One, that's none of her business and two, I would have preferred she ask me. But she freaked out when she found out that my mom and my dad's mom never got on. When my sisters and I were out of toddler stage, my mom never went to any of my dad's family events and that included holidays. When we were old enough, my parents let us choose what family events we wanted to go to and inevitably we decided to spend more time with our mother's family because that is where we felt comfortable and we spent more time with them anyway. Plus we knew that our dad's mom hated our mom for no reason. Why would FMIL freak out over this and how is that her business?