^^^ Her name is Miyazaki, one of Uchi's friends. Tomoko is always accidentally smashing up against her on the train. This actually happened in one chapter, except for the boob grab.
Ep. 12 was interesting and obviously really well made, but to me it felt kind of... out of place? I don't know; it felt weird. I would've preferred something more intimate and true to the characters to finish off the anime/season.