WMG: Princess Nine
Hiroki intentionally goaded Ryo into not balling him in order to win the game.Hiroki didn't actually care whether Ryo was playing to her full potential or not. He was actually just goading her because balling the star batter was a good strategy that was actually working against the Kisaragi Boys' team. There's a chance that if Ryo didn't change her tactics, the Kisaragi Girls' team would have won and ended up making it to Koshien.
Izumi's relationship with Ryo was more of a sibling dynamic; she only fabricated her hatred/ rivalry with her to mask how she really felt