You don't understand corroborating means. Ford knew Kavanaugh from high school, which means that she would be able to identify him. That's corroborating evidence because when she identified him as her assailant, nobody would wonder if she could pick Kavanaugh out of a lineup. It's not proof or even strong evidence, but it is corroborating. And it's independent evidence because Ford knowing Kavanaugh has nothing to do with her story.
If you really went to law school, then you'd already know these things.
It depends on your definition of corroborating. If she’s lying, nuts, or simply misremembering, the fact she knew him in high school would make her far more likely to falsely claim it was him.
You’re arguing that the fact she knew him makes it less likely she would misidentify him and mistakenly pick him out of a lineup. But that’s simply not true based on the research on how memory works, particularly when reconstructed decades later.