Puppy Palace,
I wouldn't get too upset. In a healthy dog you SHOULD be able to FEEL the ribs not SEE the ribs.
I would up her food anyway based on her breed, age, and size, like the others said. You can always cut it down if she begins to get a little chubby. I find food charts confusing sometimes - so many things to take into consideration. You could always try to put her on a scale if you have a human scale at home - this would give you an idea of her current weight if it is not time for a vet visit. Also, they would probably let you come in and weigh her for free.
I would try these things first. If she is otherwise healthy, I don't think you need to shell out for a visit to the vet just yet. If things don't improve, though, you may want to reconsider the vet.