Penn State won over Minnesota: 29-27, 25-20, 24-26, 25-20. Officially Nebraska and Penn State are co-champs at 19-1. There is no tiebreaker in the Big Ten volleyball standings as there is no postseason conference tournament and not all teams play everyone twice (Nebraska-Penn State being one of those matchups, which Nebraska swept).
Nonetheless, congrats, ladies!
Edit: That Northern Illinois loss early in the season looks strange. Just checked out the RPI, Northern Illinois is #187 (out of 334) at 8-23 overall.