Cute, but why does she always end up on her left?
She doesn't always, but she always does on the train, and often elsewhere.
Sakura gets on the train first, and she seems to like grabbing an end seat, probably because she doesn't want to be pinned in by strangers on both sides. Takamine always comes and sits next to her. She's probably sitting in the same spot, too, since she's trying to make herself easy for Takamine to find. It could be that it became sort of habit to arrange themselves that way, or it could just be coincidence. Either way, Sakura noticed that Takamine is usually on her right, so she put her cute hairpin on that side, because she wants her to notice and compliment her.