Thank you for that information and mauY I apologise for the way mey answer is printing out as there is a site issue. Sneezing can be from allergies, dryness, a foreign object in the nasal passage, virus, or even a tooth problem can cause a problem. I would not say it is an emergency if she is still eating, drinking, has no fever and is not lethargic.
Should you notice any of the above or you notice any problems with breathing such as wheezing, or sneezing blood then you will want to make an appointment with your vet. What you are describing does not sound like an emergency. It's possible the park you visit laid something down that is irritating her as well. Just keep an eye on her for now.
Here is more on sneezing and nasal discharge.
http://www.petplace.com/dogs/sneezing-and-nasal-discharge-in-dogs/page1.aspx
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