That is so cute.
I didn't see threatening at all in that picture. Her eyes are soft, her nose is not wrinkled up, her commissures are neither pushed forward or pulled back, her ears are all the way back, but not pinned or airplaned, her jaw is relaxed, and she has her head tilted back slightly, displaying her throat.
She is doing everything she can to say, "see, I am nothing to be afraid of."
Have you ever read Stanly Coren's book "How to Speak Dog"? The first case he discusses is a breeder misreading this very grin in her setter, on page 4 and 5 ( paperback edition).
It is a really good book. I highly recommend it.
-Nicole