It’s Mindy Finn, a GOP strategist. From the McMullin campaign website:
Beginning as a communications and legislative aide on Capitol Hill, Mindy quickly built a career advocating for conservative principles and candidates across the country. She has worked with both President George W. Bush and Mitt Romney to help advance the ideals of liberty and equality that she always believed set the United States apart as a great nation.
I was personally hoping for a bigger name, but she certainly seems qualified. Think of it this way, by just being in politics and policy for nearly 15 years, she probably knows more policy and the world than Donald Trump, Gary Johnson, and Jill Stein combined.
RedState also breaks down the move, and makes an interesting point:
Between McMullin’s government experience, Finn’s tech business savvy, and their youth, they are definitely a team for the modern times.
Apparently Finn has done a lot of work for tech companies. If the future of the Conservative movement is someone who served his country running with a tech entrepreneur, than bring it on.