There's nothing wrong with Twitter. It's a fantastic way to communicate with others, and get news, updates, etc.
Agree. The problem isn't Twitter, or facebook, or any of the other social media. They are useful for contacting friends, associates and for networking.
She could have done the same thing with a telephone call or email or anonymous note.
So, the problem is individual. There's no reason on earth for her immature idiocy beyond immature idiocy, and she's going to pay a heavy price for it...not just legal, but educational and a far dimmer future career.