First of all, that rat looks a little bit big for a 2013 baby. I would drop down a side or feed her less often until she gains a bit of weight. How much does she weigh?
That heavy breathing was probably her way of hissing and telling you to back off. I don't offer my snakes food while they are in shed because 90% of the time they won't eat it anyway. I will give them a meal after they have shed (NOT after they have gone clear but not yet shed). Usually shedding helps them to work up an appetite. Now, I do have one normal that eats EVERYTHING. She'll eat in shed and I'll offer her a rat while she's in blue but not if she's gone blue and then gone clear (sometimes that new skin can constrict and kill them if they are shedding and it dries around a full belly). It's also good to note that I feed live and most of my animals have a better feeding response on live. It wont' hurt to offer food, but if she's hissing, I wouldn't offer and just leave her alone until she sheds, then offer her food.