How do we legally terminate a ‘troublemaker’?

Q. I have an employee who is known as a troublemaker. When she’s upset, the whole team is upset, due to union contract in effect. I want to get rid of her. Recently, she asked for a copy of her personnel file and I haven’t provided it to her because there was nothing in it. But I have to do some type of disciplines to include in the file before I give it to her because she has never had any violations against her. What can I do to get rid of her sooner? - Anonymous, Indiana