There are two solutions:
1) earplugs
2) have her sleep in a room further away from your bedroom.
Cavaliers have noses that are shorter than would be normal if this wasn't a feature specifically bred for -- ie they have artificially short noses (even a longer nosed breed sample still has the foreshortened brachycephalic skull -- some researchers debate whether CKCS are officially brachycephalic in the strictest sense (like pugs) but they still are short-nosed). This can actually cause some very serious breathing problems in some dogs
. In most, it causes two things: the cavalier 'snort', and snoring when asleep. Some do this more than others, especially in certain positions (as with people!). As snoring is directly related to the physical shape of the dog's head, there's nothing that I have ever heard of that will stop a dog snoring. I'd be very dubious about giving any thing to change what for this breed, is totally normal. It's one of the downsides (at least for some of us, including me! I hate snoring) that comes with owning this breed.
Being even slightly overweight can increase the problem. Every study in the US has demonstrated that most people who think they have fit dogs actually have
overweight dogs -- and vets rarely say anything til the dog is grossly obese. Check the shape of your cavalier against Laura Lang's pictures here:
http://roycroftcavaliers.com/manualfeeding.htm
A dog should not look any bigger that this dog from the above link -- and this would be slightly
over what would be considered by this show breeder to be 'ideal weight'!!!
Lily was grossly obese when I got her, snored like a truck driver, so much so, and so unbelievably loudly, that I couldn't sleep without two closed doors between us. Having lost a third of her body weight, she occasionally snores and I have to give her a shove to stop -- but she sleeps in my room with the others now.
In conclusion -- walks, meals, additives etc aren't going to help. Some dogs seem to snore less -- or more -- as they get older, and some will stop or improve if brought down to a lean weight. But other then that -- if you have a snorer, best to put her further away at night if she wakes you as there isn;t much else that you can do.