Well her trying to figure out whatever it's just a friendship or a actual love would be a very fitting thematically considering the series is called between Philia (love for friend) and Eros (love for partner).

Tfw the philia love Nikaido felt was for Jun and she mistook it for romantic feelings

It is a very fitting name not only for the relationship between Kurumi and Nika but their relations with Jun an Kyou

Jun is there to make sure things are serious I think, they are going out for over a month and that is probably the longest she ever had.
And he probably noticed a change in Nikaidou's behaviour too, since she stopped responding to his calls before the phone dropped in the bridge.

As for Nikaidou's feelings, she did mention that she gets hot when she kisses Kurumi so I think this muddled feelings drama is just a set up for she actually getting turned on and making a move on Kurumi since I think Kurumi is too much of a sweety to go on the offensive

I predict a lot of drama going when Ookuma's parents discover this, I think it would be interesting too, we usually have the super supportive parents going on or it's never adressed at all and I don't remember reading many stories that get into the family drama part of coming out (if you know some please link it to me please).