If they thought she was unhinged and a danger, they would not have buzzed her in.
It could be as simple as she was calm and normal when she was buzzed in and once in she became belligerent and as I said become "unhinged"
This smells like she is has perpetually victim mentally..
They know how to work the system to manipulate the rules to get her way...
Of course I'm just speculating...
The only evidence we have of anyone acting irrationally is the principal.
“Oh, Student’s Mother didn’t sign in. I’m calling the police.”
THAT is known irrational behavior. We don’t need to speculate about unknown behavior.