As spartan initially pointed out, almost everyone in this thread is confusing sexual harassment with sexual discrimination. Almost everyone is talking as if Michaela is suing for sexual harassment and she is not. She is suing for sexual discrimination.
Sexual harassment (not what Michaela is claiming) is "hey baby nice t!ts" and the like constantly from coworkers or getting her a$$ pinched in the workplace or getting gratuitous sexual advances after she has already let the person know they are unwanted and that they need to stop or it could be the boss telling her she better put out if she wants to keep her job, etc.
Sexual discrimination (what Michaela is claiming) means that you are being unfairly treated different because of your gender. Like a woman who says she performs her job just as good as the men with the same job but is getting paid less simply because she is a woman. Or a work culture where only the men are getting promotions and women who were more deserving were passed over simply because they were women. Or the woman reporter that says she gets the crappy reporting assignments just because she is a woman even though she is as good or better than the other male reporters.
http://www.dailyrecord.co.uk/news/scottish-news/scots-snooker-referee-michaela-tabb-6384444
Per that article and what little else is available on the web Michaela is saying that she didn't get a bonus simply because she is a woman. I don't know the details but based on what is out there I am presuming the situation is something along these lines:
There is a bonus (yearly?) that Barry Hearn gives out to referees he feels are deserving. Michaela didn't get that bonus last year but other male/s who Michaela feels are less deserving did get the bonus. Michaela feels that these other male referees were given the bonus simply because they were males. It was favoritism because of their gender. This would be a form of sexual discrimination. Michaela threw a fit about not receiving the bonus to Barry Hearn. For whatever the reason, Barry was pissed at Michaela for throwing the fit about it and didn't use her as a referee any more in world events that year, kind of like taking an employee off the schedule and giving them no hours. Michaela realizes after months go by that she is basically screwed now and likely won't be getting much work from Barry in the future so she decides to go ahead and just quit and sue Barry for sexual discrimination instead. Might as well in her mind since he isn't giving her much work any more anyway so there is nothing to lose now.
So the question at hand is did other male referees who were less deserving get this bonus simply because they were males, or said in another way, was Michaela just as deserving of the bonus as the males that received it but she didn't get it because she was female? That is why they are in court now (or at least that is the only part that we know about at this point).