So it’s okay then?
Ok???? That is a highly subjective response and depends on the attitude of the person responding. So lets look at a more objective question. Was it lawful?
Lawful, yes. She was on restricted public property (school) that had set a requirement to be on that property. Schools are not open to the public. Yes there are exterior areas that the public is allowed to access but the school proper is restricted access.
When she did not comply with that lawful requirement (making), law enforcement was called and responded, and informed her of that requirement. The LEO gave her the option of leaving the property to avoid the arrest. She then CHOSE to remain, after being lawfully trespassed and when she did, she crossed over into an illegal act of criminal trespass.
The arrest was lawful.