Just to show how wide the range of possibilities is:

When I was 12 or so I happened to be hanging around a sandbox with some other kids and somebody started throwing sand. I eventually managed to extricate myself from the battle and brush myself off, but for the next half hour or more I'd randomly smell something like coffee roasting. I asked my family if they smelled it too but they just looked at me like I was crazy.

It was only after a good deal of nose-blowing that I managed to free myself of the smell. I'm pretty sure I'd gotten some sand in my nose and whatever was mixed in with it was working havoc on my smell receptors.

I think serafim's suggestion, getting her nose and sinuses checked, is well worth considering.