Honestly, this friend seems like she's making drama for the sake of drama
I mean, a really pent up woman had her first taste of a man wanting her in YEARS. I feel like it's a bit unfair to say "You want him because he's your student, girl you're fucked up"
Like yeah, that's kind of the premise of the story, teacher wanting her former student's dick, but they're acting like him being her student is the entire reason she wants him. She wants him because a young guy walked into her room, pinned her to the bed, and was about to help her release years of frustration.
The words she tells her friend are "It excited me because it was animalistic. It was rough, simple, and had a good atmosphere" and the friend just goes "So you want him because he's your student?"
I get the whole point of the manga is "Teacher begins dating her former student" but it still feels like the friend is twisting FMC's words