Is she due to shed? The skin loosens around the tip of the snout first, and sometimes it irritates their nostrils and causes them to sneeze. If this is the case, then things should get back to normal once she sheds.
If you put your ear near her, can you hear her making tiny clicking or wheezing noises? It's possible that she might have the start of a respiratory infection, but I don't think this is likely. If she was coming down with something, I'd expect her to be much less active and not more active.
A third possibility is that she's going to lay eggs. Has she been anywhere near a male? Females get a lot more active as they come up to laying time, as they look round for a suitable place to lay.
