Aww, sorry you haven't been feeling well! Hope you're better now!
Ribs can be totally normal, especially as they are growing. I think often people freak out a little too much about seeing ribs on our animals. You have to think, lots of healthy kids show ribs! They are so active and its all a part of growing. Athletes show ribs easily, too. I'd rather a puppy be lean than too chunky. Don't stress, a little ribs are ok, especially when they are taking a breath in. Taking in the overall picture of the dog is a much more accurate way to judge physical fitness than by judging on the sight of ribs alone.
If she's more active lately, you can easily increase her food to compensate. I always look at my dogs to judge when I need to up or cut back on food. If they are showing a little rib, I don't worry unless we are increasing our activity. If they are showing absolutely no rib (even the last one) I feel them and if I have to press hard to find rib...wellll woopsie, time to cut back on food, lol.
Here is a good example on a 4mo boxer pup, showing exactly why it isn't accurate to judge if they are "too" skinny based on the sight of ribs alone: