It was the fall of 2012, and Kathryn M. Walker had her law degree. She had her license, practice area, job and clients. Now she needed to add another crucial piece to her career: a mentor. So she called Sarah Zearfoss, the dean of career services at her alma mater, the University of Michigan Law School. “Do you know anyone in Chicago who is a bada-- female litigator?” Walker asked Zearfoss. &ldquo …