Something i never noticed before at the start

Theres kind of a really small hint at Mrs. Olson being an alien when they're in the faculty lounge at night with Miss Drake going over what things they can and can't get.

Miss Drake tells Mr Tate he can't have a field trip and Mr Tate gets frustrated, then she tells Mrs Olson there wont be any new computers and Mrs Olson kinda pauses with no emotion for about 2 seconds as if she doesn't know how to respond immediately, but then finally expresses disappointment, as if she just remembered how the other teachers reacted to getting turned down.

Its a little small thing but its something i never picked up on until the other day watching it, cause they tried to keep Mrs Olson being one of them a surprise until she kills Miss Drake.