Meh, I'm on the "dud train" with this one too. For as long as it is, so very little happens, especially compared to the usual Mochi stories. I don't think the length added anything to some pretty one-dimensional characters. She rolled out all the tired old tropes here - the "should two girls be doing this," the "what are these feels?, " the "I'm ok if you'll have me," etc. And the yuri at the end is kinda perfunctory and robotic. It's not clear at all why the kouhai should be attracted to the senpai, since as far as we can tell her only redeeming quality is that she shows up to practice.
All that aside, even if she can't stand up for herself face to face, since it's the first years' responsibility to clean up can't she just drop the mop, walk out, and let them take the heat? And more than that, isn't Tsukioka a first year, so shouldn't she have had to clean up anyway and is not exactly doing a special favor by helping?