My dogs both eat about 2 cups of food per day and their food is around 400-430 calories per cup. Chase is the bigger one and gets rounded cups so he's probably getting a little more than Lark, who gets level cups. Neither is super active and seem to maintain their weight within a few pounds at that amount. One weighs about 65 and one weighs about 85 pounds. A little more or less here or there usually brings them into line if they get off their usual weight. You can add unsalted canned or frozen green beans to their food if it makes you feel better that they're getting a bit more into their tummy. If she gets a lot of treats, some have more calories than others, too. There are treats with very few calories in them you could look for and raw baby carrots, blueberries or other things like those can be used (not grapes).
It's hard to compare what one dog eats against what another eats, since there are foods of all different calorie levels and dogs of all different activity levels. I do not often have to adjust their food levels. If there's a Petsmart near you, you can take your pup in and put her on the scale near the vet area without being charged for a vet visit. My pet food store has a scale where you can weigh your dog and I'm sure my own vet would allow me to walk in and weigh my pup without blinking an eye, in case you want to see what her weight is doing now.