Well, as I would always say, it's better safe than sorry so it's good that you're taking Doris to the vet to get this checked out.
When does she sneeze mostly? Is it when she eats? Hay allergies are unfirtunately more common than you might think in piggies and so this could be a factor. There are dust extracted hays out there (I think the Oxbow Timothy Hay is a good one for that) and your vet might consider steroids...
Other than that it could be a URI or other infection so you are definitely doing the right thing by taking her to the vet. It must be remembered though that piggies do and should sneeze every now and then and that's normal but if Doris is sneezing frequently or when she is doing something in particular then this could be a symptom.
Best of luck and fingers crossed for Doris.
P.S. she looks really cute in that video