Constantly making verbal observations to a young girl that she is pretty is not a compliment. Instead this is subtlety telling her that her primary value is her looks: her appeal as a mate so that she can attract a suitable male to support her, ostensibly because she is incapable of supporting herself.
And in turn, when she internalizes this idea at a young age, she becomes angry inside at both the message of her being inferior and incapable of self-support (which her own heart and mind know as untrue!), and also for having suppressed her own entirely human and natural scientific exploratory interests of childhood at the behest of parents, other relatives, or peers.
At worst, out of jealousy she then becomes cruel in turn to her peers that haven't been subjected to the same indignity, criticizing their lack of self-consciousness when they are far more interested in frogs and kittens than in catching the attention of a boy, and thus spreading a horrid viral mental disease of female domestication. In some circles, this female passive-aggressive behavior has been identified as bullying.
Look, it is okay to be pretty. Good grooming is important to both females and males; grooming reduces disease and fosters social bonds so that we can function in society. But handsome looks are far secondary to being capable, intelligent, and creative.
Tell her how smart she is. Answer her questions about how the world works, about animals, insects, reproduction, and the color of the sky. And if you don't know the answers, take her to the library or help her use Google search. Praise her curiosity.
Don't set too close limits. Let her push her boundaries, even at the risk of danger. It is far more satisfying (and more beneficial to our species overall) for a human to live a short dangerous life filled with exploration, than a long safe one ensconced in a locked castle.