I'm not sure if it's her that Tsubasa wants Sensei to lose himself on...exactly.
There could be cameras in that apartment that Sensei got from Touka, and Tsubasa already has checked out Sensei's room while he wasn't around (not to mention spied on him and Chika before). Frankly, her getting Chika, Chinami, and Tsukasa (and probably Yasu, albeit that might be more Touka's idea) all in that building with Sensei, could imply she's wanting a certain form of entertainment.
Not to mention possibly blackmail. If she wanted, she could have recordings of Sensei and New Maya, now.
Tsubasa seems like a bored horny voyeur in a way, that's definitely sexually frustrated:
She however treats Sensei more as a puppet than a threat or love interest, albeit she does claim to want more of an equal relationship with him.
In reality, she may just want a main character for her steamy soap opera...