Puppies generally eat between two and three times a day (preferably 3), and Boxers being such an active breed do need quite a bit of food. Boxer people I know give their pups about 5-6 cups a day, which is about 2 cups per meal. Purina Puppy Chow isn't a high quality food, so it's going to go right through her system thus making it harder for her to gain weight. I'd recommend feeding something of higher quality, which wouldn't be anyhting that you can find in a gorcery store. Nutro (Natural Choice or Ultra) is a step up from Puppy Chow and can be found in PetsMart aswell as Petco and any other smaller pet store. Natural Balance is even better than Nutro and I think can be found in Petco (I'm not from the US, so I'm just going by what I've heard). If you can find Canidae, Innova, California Natural, etc. those would be even better but if you can't, Nutro or Natural Balance (which ever one is easily available to you) would be a great start, in my opinion. Of course, you don't have to change her food if she's doing okay on it but in the long run it would much better for her. Good luck with your pup .