Please review this link from the DFEH
Even if the DFEH determines that there is no discrimination, if you complain to your HR department that you believe you are being discriminated against by your supervisor, based upon one of the class-based reasons that I previously described (i.e., race, religious creed, color, national origin, ancestry, physical disability, mental disability, medical condition, genetic information, marital status, sex, gender, gender identity, gender expression, age, or sexual orientation), and after complaining to HR, you immediately complain to DFEH, then you are also protected, as a whistleblower, from further actions by your employer which appear to be retaliatory in nature (Cal. Labor Code 1102.5).
You need a good faith reason for your complaint (i.e., an honest belief that there is something more about your supervisor's conduct towards you that cannot be explained by mere personal dislike of you. Ironically, personal dislike by a supervisor does not violate the law. Only discrimination based upon class is actionable in court.
So, you don't really need to prove discrimination. You can show a pattern of negative conduct by your supervisor towards you, that cannot be explained by any reason other than discrimination.
It would be great if you had a "smoking gun" (e.g., an email with discriminatory language, or a witness who has heard the supervisor say something discriminatory about you). But, if you don't have it, then all you can use is what you do have, and if you complain to HR and then complain to DFEH, then further negative conduct by your supervisor would be retaliatory even if there is no discrimination iknvolved.
Hope this helps.