In my experience, attitude trumps IQ in pretty much all situations.

Most humans are average in what they do. Potential doesn't matter, only reality does. Focusing on potential is what arrogant people that are lazy like to do, but mostly no one else cares.

You are the perfect example: > I am now a below-average performer at an elite company

Teach her to have mentality of curiosity, lifelong learning and humility and everything will be just fine.