What I mean is that she doesn't enjoy the "ntr aspects" of sex, like cheating and being shared, in this scene she just realises the mc is bad at sex and probably starts considering leaving him. The writing makes it feel like she has a vanilla approach to relationships, and is just looking for the better partner and the teacher makes her value sexual pleasure over whatever the mc can offer. It feels more like she dumped him than anything else.
And I know ntrman can write games differently, adelaide inn is a great example where he writes a female character that makes use of ntr and still keeps the mc involved.