yes it can be quite common in shihtzu and all flat nosed breeds....i suggest you get some infant vapour rub and a humiderifer if you can as when she is teething it will get worse as the nostrils close when teething and as she already has a problem it will excebate it.....
if you keep her in a pen or crate for sleeping make sure you have one with a door if possible as when you lift her up her head will go back and close her tubes causing her to faint so keep her at the same level as possible no jerky lifts rub some vapour rub on her chest which will open the passageways and help her breath check her as she gets a little older when she is teething you may have to use the humidifier....
i am not in favour of the surgery if you can avoid it do so but if its genetic then i'm afraid it will have to be done...never contemplate breeding from her as this is an in herited condition...and you will breed unhealthy puppies that will have to go through a lot of distress....
when she snorts if its prolonged put your fingers over her nose so she has to breathe through the mouth as the tongue gets stuck up the roof of the mouth if its dry with panting ...dont worry just be vigilant...
she is very little is she the runt of the litter i know some breeders like to call them imperial but in truth they are the runts and all the health problems that come with being so small and fragile...
rose