Hello and thanks for trusting me to help you and Leelee today. I am a licensed veterinarian with over 30 years of experience and would be happy work with you.
The two things that come to mind is that she may either be having some flatulence or her anal glands may be full or impacted. If a dog is passing gas, and it is not something that she is used to, it may startle her out of a sleep. Anal glands, on the other hand, can be very uncomfortable and may be waking her up if she feels discomfort because of them being too full. Even if they are not impacted or full, some dogs, when they are very relaxed or sleeping, may express some of the fluid from the gland and that is what she is smelling.
It would be a good idea to have your vet check her anal glands just to be sure they are not infected, impacted or just too full and need to be emptied as if it is ignored, it can lead to an anal gland abscess.
Here is a link with more information about anal glands in dogs. LINK HERE
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.
My posted replies are for general education only and not meant as a diagnosis. Only after a thorough veterinary examination can a diagnosis for your pet be made and specific treatments be advised or medications be prescribed.