Hmmmm... I think it all comes down to how you portray Sakura tbh? Like I don't think there's any outcome where Rider wouldn't get into one of Sakura's fetishes (she's such a wifegirl <3) but I could see her having different rationalizations.

If Sakura just admitted this is a fetish thing for her, Rider would also say this is a fetish thing for her too.

However I was talking with a friend yesterday about the idea of Sakura at first getting into the kink as a way of dealing with her fears of abandonment - "Fattening up my boyfriend so he can't run away" kind of thing. And if that was the case, I could see Rider trying to intervene... by eating all the food and fattening up herself as a way of "protecting others from Sakura".