As others have said, check her BMI (though also be wary that a really tall and really overweight child, even if the BMI is okay, can also be unhealthy).
One of the dangers with overweight girls is that it causes them to go through puberty earlier than they should, which has various knock on effects, including limiting their height.
I keep an eye (without her knowing!!) on my DD8's weight as she takes after my DH's side, who have a short and stocky build.
She is currently around the 75th percentile for BMI (25-50 centile for height and 50-75 percentile for weight!), but has had periods where she's neared the 90th percentile.
As a comparison, she is currently just over 4 stones...
My 6 year-old DS is just over 3 stones... (BMI around 17th percentile 😆).
Edit: Sorry, just seen your updates.
What I do with my DD is go with the idea that no food is bad, but some foods do more for your body than others. Ie chocolate gives you a little bit of energy, but only for a short while, might be better to have something that fills you up for longer.
When coming in from school, I give a snack with protein, so like breadsticks and peanut butter, carrots, banana, but also serve it with something like 10-15 smarties, so chocolate is not forbidden, but not much. If they ask for more, say something like that's all for today, but can have more tomorrow.
We have dinner quite early, and then maybe a small yoghurt after. If still hungry at bedtime, they can have a cup of milk and fruit.