Gosh I'm sorry to hear this about Tootsie and hope that your vet can find out for sure if she is sundowning or it is something else. Other medical conditions can cause night terrors, disorientation and mimic CSS. Be sure you tell the vet every single thing about her and any little thing that is different to be sure the vet looks at all possibilities. I hope you can find out for sure what it is and can get her some help and she can feel better and rest soon.
The Pet Docs
BTW, welcome to YorkieTalk.