While she was at the first casino, she accumulated a list of "elite players" as part of her job. When she went to the new casino, she contacted those high stakes players to try to get them to come to the new casino. The first casino is not happy about it.
So, what can employers like the first casino do to protect themselves from things like this? Well, the obvious answer is to put a restriction in writing. According to the article, the employer did present the employee with a noncompete. But, she said she didn't like getting "harassed" to sign it, so she quit.
Ideally, the employer should have made the noncompete a condition of starting the job. The employee claims she built her book of business on the job - something she could not have done if the casino had simply refused to let her work without first signing the agreement. The noncompete could also include nonsolicitation provisions, and identify the customer list as confidential proprietary information.
Now, the parties are stuck battling it out in court.