She is 9 months. Right now she weighs 42lbs.

She looks fairly well developed for 9 months. I don't imagine she will get much heavier. She might go to 50 pounds but it's hard from those pictures to tell whether she should go to 50 pounds or if she may be a little overweight if she puts that much more on. Her growth plates look closed so she shouldn't get any taller.

She looks good to me (not an expert).   As a point of reference, our female was 44lbs at 9 months.  She's not much heavier now, but we try to keep her lean.

On an unrelated note, your prong collar is not fitted correctly.  They should not be loose.  They should be fitted tighter and very high up on the neck.  Try removing one or two links.

A correctly fitted prong will give you significantly better control of your dog. It can also allow you to use smaller corrections to get the same result.