Try Wednesday 3:30 PM. It doesn't fit exactly because the guy she "likes" (I'm not sure that's the best characterization) is her ex and he is a bit of a jerk (he dumped her so he could date her coworker), and the ML doesn't start out liking her from the beginning. He falls for her during the process of helping her. But the ML is very supportive, the ML does develop secret feelings, and the FL does realize her feeling pretty late.
Also these aren't Korean dramas, but consider trying Japanese drama Kimi Wa Petto (2017) and Taiwanese drama In Time With You. In both cases the ML doesn't exactly help her try to win the guy she likes, but he is secretly in love with her for a long, long time, he is very supportive of her and consoles her when her love life doesn't go well, and the FL realizes her feelings for the ML very late in the drama.
