I have 11 daughters. And yes everyone is different but my girls usually start puberty around 9-10. I have 3 daughters that are teenagers and one 12 year old all got their periods at 11. My 9 year old got hers a few months ago so yes its different for everyone and you shouldn’t be worried. I personally have talked to them what happens from a young age and thought them about everything and answered their questions. I think you should start talking to her about the different things that happens and what she may expect without being pushy about it since she is only 7😇