"She is lucky to have a boyfriend like you. There wasn't any guy of my age with similar talent when I joined. You two are lucky to have each other."
Shiba's opponent was really jealous of Eini. Not because she liked Shiba, but because she would have loved to have met a guy of her age that could match her in talent, and then became a couple of lovebirds.
Although at higher Ranks, age didn't matter that much, she had never been willing to be with those older than her. That rejection was greatly increased by the fact that the only one that could beat her while being at Rank 2 was Eini's previous opponent, who always acted like if he was a great senior and liked to teach lessons to others as if he was that much more experienced. That man gave Shiba's opponent such a bad impression that she swore to never date someone older than her.