Oh Wendy what a shock but massive positive thoughts for your girl.
A similar thing happened to my sisters whippet (actually you met in haigh hall once) just before Christmas and I did the emergency run to the vets with him thinking he was not coming home
but like Millie he is a fighter and is still going and enjoying life! They said they thought he had had some sort of fit or mini stroke so they can recover even when you think they are soooo poorly.
Lots and lots of healing thoughts for Millie.
Amanda & Poppy x