Attempt at a positivish spin:
Sensei was into Suzu (page 12, "I was always watching you"), lied/misled her way into being a tutor, and "tutor". Suzu isn't without agency: she asked for "sex appeal" lessons, and agreed to go further... and she had her own goal, appealing to Hayato (her male friend), so there's a good reason there wasn't any further relationship: Suzu was headed for someone else.
Except she found she had more chemistry with sensei than with Hayato, is still juggling a torch, and Helpful Mother sets them up again (probably not deliberately, though honestly I wonder about her.) Page 14, Suzu uses sex-appeal! ... and going by the mutual blushes, and the last panel, it is effective.
Page 15 tells us that sensei had moved on (just like Suzu) and has a new 'student', Rena. But the first and last panels are in parallel with Rena primping, and Suzu is doing things to sensei even as she thinks "...and rots." Dark thoughts or not, sensei isn't exactly pushing Suzu away.
So it's like she's in a relationship with Rena (probably multiple encounters, given Rena's enthusiasm, vs. just once for Suzu) but her ex/one-afternoon-stand whom she never got enough of has shown up and is having her way with sensei, and sensei's life has just gotten really complicated.
Mom the matchmaker?: so, sensei lied to Suzu, but did she lie to her mother? "Even your mom just said I'll leave it to you", mom knows the real Toudai, mom is shown laughing on the couch while Suzu is 'initiated', mom suddenly points Suzu at sensei again out of the blue. It's an odd choice of framing, at least.