I don't think Karin is fooling around, but this chapter raises the possibility of an interest twist of sorts in which the question "which one is love" also applies to the potential love interests. Like Minato in this chapter, there is the possibility of them all who were coming from a really, really innocent place before to suddenly realize "oh shit wait this is for real- this is love! roll credits". Not sure this is the route I prefer, though. In any case I'm certain Karin has some perfectly reasonable in-universe-shenanigans way of "redeeming" herself. Or they just straight do it, I am perfrctly fine with this as well.
Also I feel like an F for glasses friend is warranted.