It’s not, I’ve had several talks with my kid about this through their life so far and they’re around that age.
They need to know that not every adult is safe. That there are adults that want to hurt them. This is the truth regardless of gender.
Internet safety is a big one. Also teaching what to do if someone tries to pick them up, if someone wants to know more about them or if they feel uncomfortable, etc.
I talk about how different groups of people are sometimes treated differently in our society. This includes how women are treated. What slurs are and why they’re harmful.
It’s all part of a larger conversation about the truths of our world. At 9 years old, they probably have already picked up on some of this. Maybe start with asking what they perceive about this already if anything?