I got the impression that, at first, she was pushing Tsukasa into this to keep all her friends normal because she knew that Tsukasa liked Nadeshiko. If she could make Tsukasa 'normal' then the friendship between the three would continue. Maybe different interpretations?
I'd say it's certainly part of it, I think where we differ is our interpretations of the characters and their reasons for acting but that's only a guess really.
Kotooka does want her friends to have some semblance of "normalcy" in order to maintain the friendship that all three of them currently have. But that's because they're in a love circle rather than a love triangle, in my opinion a love triangle implies that there are two people competing for the same person rather than the situation they're currently in. Leaving my opinions on that aside, is the biggest issue for any of them getting in a relationship with one of the others is how much it'll change the group dynamic.
This is easiest to see with Kotooka (Who had the single best chapter so far) as she's in the precarious situation of realizing the feelings of both her friends. Kotooka is in love Tsukasa but recognizes that she doesn't love her back, as she has feelings for Washio. From my understanding Kotooka's dilemma comes from wanting her friends to be happy but she can't act on any of her feelings as that will leave someone out in the cold.
By not accepting Washio's feelings for her and not acting on her own love for Tsukasa she risks pushing them towards each other which would leave her to wallow in her own unrequited love and possibly breaking Tsukasa's heart as Washio doesn't recognize her feelings for her. By accepting Washio's feelings for her she takes the object of Tsukasa's love, causing both of them pain as Kotooka has to accept what she's done to the person who actually holds her affections.
In Kotooka's eyes "normalcy" is a far better option than possibly destroying their friendship. She wants to engineer a situation in which the three of them can stay together for as long as possible, and if that means forsaking the romantic feelings of everyone? She seems to be that determined at least.
Now onto other things:
Did anyone else notice how Subaru dressing as his sister is very reminiscent of his namesake constellation? Subaru being another name for the Pleiades, or the Seven Sisters/Daughters of Pleione. As well as taking the Japanese meaning of the word which is "Coming Together." Seemingly he wants to be as close to his sister as possible, which is why he dresses as her.