Dear M.,
I would have to assume that you have brought your concerns to your daughter's pediatrician. What does he or she suggest?
It would seem that you are doing all the right things, however sometimes children do go through those very "awkward" years in growing when they seem to hold onto baby fat longer than other children do. If your child's doctor has tested her for thyroid problems or any other physical reasons regarding her weight gain resulting in no answer, then I would tend to lean more on the side of it just being a period in her life where she is growing up but difficult to shed the extra weight that she has right now.
I would highly recommend, if you have not already done so, that you have her doctor test her for any possible thyroid problems, metabolism, or more in depth reasons why she seems to be active, eating healthy but still gaining weight.
You definitely don't want to make this a huge issue to her where you are watching every single thing that she eats and also others outside your family, such as your neighbor. You would be surprised how much kids pick up on what you think, feel, and react to in situations like this one. She might possibly be consuming food that you are not aware of simply because she is being watched so closely. Be very careful...girls are more delicate about this issue than boys.
I will end this with my advice that you seek the help of your daughter's pediatrician, have her tested, and then go from there.
Hope this helps and I wish you much luck.
T.