I don't think I've ever heard them unless they are slightly grumpy huffy. Put an ear to her body and try to find her lungs to see if its clear or rattles. It may be perfectly normal for her.
I probably do hear it but don't notice, usually when the Hog Island is perched on my head, she sends a strong cold little blast of air right into my eyeball or down my shirt. Surprisingly strong little lungs/nostrils!