For that particular situation, I'd stay silent. I agree there's a risk, and that this is a problem.

Longer term though, I'd make sure we hire female investors into my VC fund. I'd take them along the journey of investing with this startup, and if I felt a female CEO needed to be replaced with a man, I'd discuss this with my investment partners. Any harsh feedback, if given, would be coming from all of us, and a mixed panel would be harder to accuse of sexism.