The one thing not to do is tell her she's overweight. If she is as big as you suggest she'll definitely know and probably gets teased at school - even if she doesn't let on and teachers don't notice.
I speak from experience here. I was a slightly bigger than average kid. Not overweight per se, but taller, bigger and squarer than my peers.
I can, to this day, remember my mum telling me at age 5 that I couldn't wear a skirt to school - only a pinafore - as I was "too fat". She'd constantly compare my frame to that of my best friend, who was very slender. And, at age 8, I was put on a diet - the first of many that my mother insisted I followed. My mother channelled her own deep seated unhappiness in her body onto me, not that she realised she did this.
I look back at pictures of myself at that age and I could weep. I wasn't fat. At all. But I became convinced I was and adopted the approach - at a similar age to your daughter - that "oh I'm fat anyway so it doesn't matter if I eat a load of shit". That in turn - by age 11 - turned into binge eating. And guess what? I did then become fat, and the cycle went on.
Obviously your daughter is a little different as she is, apparently, overweight. But I wonder if you have projected similar things onto her. You say you used to be overweight, you're quick to say you weren't overweight as a child, and you mention right at the start of your OP that your daughter - like you - carries her weight on her middle. Can you see why I wonder if, subconsciously, you've helped to create this situation in a similar way to how my mother did with me? Maybe, maybe not.
What I do know is that making her feel shit by calling her out for being overweight will not help. She's a little girl, not an adult.
It's great that she's sporty. That could also be marking her hungry though. Children need a surprising amount of calories, and they need plenty of fat too. Low-fat diets are not suitable for children. Maybe also find out about her favourite sports stars and if they have any favourite nutritious meals. Make them together and explain why ingredients like nuts or tomatoes are so good for you.
I'd also be binning the low-fat, high carb things you mention and focus on providing more filling meals that include more fat and protein and are lighter on the processed carbs. If she's hungry when she gets home from school, provide her with a meal earlier.
Also is she getting enough hydration? Perhaps you could get her and you or her and her siblings some of those bottles with markings on them to make sure you're all drinking plenty. Make it fun to see who can hit their daily goal.
As others have said, I'd focus on the fact that it's so wasteful that she's not eating her meals because of all the snacking. Tell her this and ask if she's snacking because she's really hungry or just because she's bored/because the snacks are there. You could refer back to the sports people and say how they have to leave plenty of room for the protein and veggies and things and that's why they can't fill up on crisps. A decent meal helps them perform better
Finally, make sure you're modelling what you want her to do. You should be eating more or less the same meals as her and eating in front of her - not skipping meals of having something different. I don't know if you do this or not, but it is essential to set an example of proper portions, proper food, proper time etc.
You will help your daughter to overcome whatever challenges she's facing by making her feel better about herself and her body, not worse. Don't comment on her body shape, size, appearance, weight - whether negatively or positively. Praise her instead for working hard, being kind etc. And, of course, if you think there's a medical issue at play or if her weight is truly huge then you can speak to a GP about it. However, it doesn't sound like that's the case