[oncelurked]

Quite honestly, if Pi Phi doesn't list her on their website, it's likely a mistaken claim. I've heard of Theta claiming her as well (search with her name in quotes, and you'll likely find something here). Most, if not all GLO's, want to recognize these women if they were members of their organization.
As I posted earlier, Sandra Day O'Connor had no opportunity to join an NPC organization as a collegiate, and since she also attended Stanford for Law school, she had no opportunity then, either. She may be an alumna initiate, but since the GLO in question doesn't list her, I doubt it.

edited for emphasis