Perhaps this comedian's mistake was advertising it as a "girls ONLY" event. They could have avoided stating this outright, maybe advertise it as "Girls night" not "Girls ONLY". And then if a few men decide to see the show anyway, they could have just been accepted in for the show without anyone making a big deal out of it. It could still be predominantly a "girls night" event, even if the few men decided to watch the show. They might be the odd ones out, but at least they weren't specifically discriminated against. What harm is having a few men in a "Girls night" event?
I see billboards and commercials promoted by divorce attorneys who represent "male clients only". And vice versa, there are "female-clients only" divorce attorneys. So far I haven't heard about them being sued. However, I am in FL, not CA.
There will always be men-only, women-only services and meetup groups. I don't think the intent is to discriminate. But in CA perhaps it is best never to promote or advertise the group as "men only" "women only" etc. It will seem like gender discrimination to some people, even when that is not the intent.