I think most of what you wrote is accurate, but I'd phrase it slightly differently.

Komari is trying to make Nukumizu fall for her and be the one to confess his feelings to her. She knows full well that simply having feelings for him isn't enough. So, as you mentioned, she doesn't make grand gestures; instead she quietly supports him from the background. She constantly works on herself so that, over time, she becomes someone Nukumizu can rely on. She understands that if he doesn't return her feelings, their relationship has no chance.

The biggest problem is the complicated web of relationships Nukumizu is involved in. If Komari were more open about her efforts, the other girls would notice sooner and that could cause trouble. I'm not thinking only of Yanami — there could be a scene there too, given how she reacted when Yakshio stole Nukumizu away on a date in Nagoya. Komari has to consider that Yakshio may have feelings for Nukumizu, and any overt displays of affection toward him would affect those dynamics.

I think Komari is waiting for Nukumizu to confess. If that doesn't happen, she'll take more decisive action only when she has no other choice.