I have a slightly different opinion and I think you recognising that your DD may be overweight is a great start - there are many many children who are overweight or obese and there parents are in denial or fail to notice it and this ends up with them having type 2 diabetes as they become teenagers. One of the main risk factors is waist circumference so if your DD is carrying fat around the middle then I would be keeping an eye on her.

I make sure every 6 months to year we weigh and measure the kids at the GP who has a record of their growth. I can then see how they are tracking in general but also if there are any significant increases etc. My DD1 is naturally lean like DP and has always been above average height and below average weight. DD2 is like me although above average height, she has my stocky, muscular build. I put on weight easily so have been keeping an eye on her. She has trimmed down significantly this year at school though as she is running around a lot more. After school I make sure that we don't go straight home and that we do some form of incidental exercise. I think the key is making sure they don't eat too many treats and that they move - in general, they don't stay sitting for more than half an hour at a time. Even if they are watching a dvd, I pause it in the middle and make them come down to the kitchen and get a drink or a snack.

It sounds like you are on the right track though, you are aware, you are encouraging activity and you are making sure she is getting healthy food. Just keep an eye on any changes.