I'm in two minds about her approach. One the one hand I feel it cheapens the image of female hackers. But on the other hand I want to congratulate her for exploiting a stereotype to her advantage.

It's just a pity that the tech industry as a bias to begin with. :(

Yes, it is a bit sexist. However, in reality, people are sexist and most IT or security people are male, so she could distract some of them.

Using distraction and misdirection is a useful tool, something male hackers would find harder - all the more reason to add more diversity to your pen testing team.