"Since children don't have free speech rights, I reject the premise of your question."
We aren't discussing a child. We are discussing a young woman. My premise is just fine, thank you.
Care to answer the question?
"However, school administrators act "in loco parentis," and courts have recognized that they enjoy the same ability to limit children when they are at school that you do when they are at home."
And I would expect them to exercise that authority with responsibility. This was not the case here.
"She is still under the jurisdiction of the school. When she gets her diploma, she is free to do and say whatever she wants."
So, until she gets her diploma, she has no right of free speech? That's very bizarre thinking.
"If she enters the world of the military, she will find that she had more "rights" when she was a student. And, depending on where she chooses to work, she may find that some companies will limit her right to speak about certain things or to proselytize on company property."
Who said anything about her entering the military? That's a pretty huge leap from what we're talking about.
And despite the fact that there are limits to what can be said on company property, employees still have freedom of speech. Any company that interferes with that may find themselves in court. For example, employees have the right to express religious views on the job. That is protected speech.
"Even as an adult, one may exercise one's right to free speech, but there may be consequences if one does."
No one's arguing that there are limits to free speech. What seems to be clear to the overwhelming majority of people here and seems to escape you is that this young woman was deprived of her free speech rights. She did nothing to come up against those limits.