She may have just committed a fallacy in truth.
That doesn't mean telling her so is the right choice.
If you don't address her experience, you're missing the point.
You can "believe" all kinds of things without feeling them and living them out.
In her case, skeptics may believe they are not fundamentally sexist. But her observation would then be that this belief is only skin deep. It should trouble the skeptic that an observer finds their community sexist, and trigger a crisis in the belief.