Senua, we are not negative. I for one thing that stimulating a child's intellectual side is a great thing in any case. We have not said that she probably isn't clever. It is perfectly possible to be clever and still not on the G&T register in one particular school.
We just ask the OP to provide information about how her dd might be regarded as G&T in more general terms, in order to formulate a more helpful answer re what she tells the school. Because if the school go very ambitious, going on their view of what is G&T, it could either be too little or too much for the child, depending on how she fits into it. Better to let the school decide an appropriate level imo.
But most of us would probably agree that being clever is something positive and needs stimulating anyway.
Having now had the OPs reply, I would say that whether she is or not, there are clearly lots of positives here that you can build on. Strictly speaking, you don't need to know her IQ rating to encourage an interest in the Tudors, as it is clearly going to be something that gives her great joy in any case. I think your desire not to overload her is a good idea, but there are so many ways you can encourage her talents without making her feel overworked. Often the best things I have been able to do for dcs have been fairly casual things, like passing the book case and saying "this is one I think you might enjoy". Or chats on the way to school. Maybe telling an anecdote out of a book to whet their appetite. And of course taking them both to any exhibitions etc that I could manage. Dd I think is someone who would be regarded as G&T in many schools, ds is in one of the bottom sets, but they have both shared an interest in history since the Reception years and I think it is a great thing to have.