It's because chapter 1 was going with the Meguro angle of "I'm only fucking these guys to be accepted." and chapter 2 shows her delight in being accepted by the MC without spreading her legs.
But here we are in chapter 3 where she throws it all out the window by asking to get railed every passing moment. It would be funny if the developments of the first two chapters haven't happened yet but that's not the case here. It's like the author can't decide if he wants to write a wholesome girl or a bona fide slut. Everything about her is iffy.
Just like that one guy said, if they get into a little fight and she starts to believe the relationship is over, is she going to accept some guy's advances to avoid being alone? Is she going back to being the class bicycle? I can see it happening with the way she's presented so far.