[误] Falling in love with Helen simultaneously makes these two good friends become competitors in love.

[正] Falling in love with Helen simultaneously makes these two good friends become rivals in love.

注：rival in love 是固定搭配。而且，competitor 多用于比赛等特定环境中的竞争对手，而 rival 的使用范围则较

为宽泛与笼统。例如：business rival(商业上的竞争对手);a violinist without rivals(无与伦比的小提琴家)等。