I mean, that is how the scene is, she made a rash decision in a moment in which she was not confident she could still have him if she didn't do something that drastic. She's playing into a common portrayal of how men think, with their dicks. She's going for the more immediate sexual route to win him over and avoid losing him. Then comes the later scene in her dorm, in which we start to see the 'sex = happy Sensei' mindset take hold, as she feels safer about him leaving than in her initial scene and feels she can slow a tiny bit, and finally the big change to how she is at the end of current content at the beach, when Kirin gets involved, as she realizes just how dangerous their relationship could be for both of them given who Sensei is outside that relationship (it takes one word to his superiors to have the entire thing blow up and Kirin, at the time in question, had both the motive and the knowledge to make that happen if she wanted).I think the main adjustment to the dialogue is for him to be the one to kind of direct the dialogue as her doing these things would make him happy.
Right now, she seems more of the instigator so I think the dialogue just needs to be altered so it's the other way around in a sense.
And getting her to think sex=happy sensei would actually make the the flow make even more sense. Especially if he's the one that kind of sets it off accidentally.