In terms of romance this really isn't Kokoro x anybody. She's becoming frenemies with Cirno, and seems to see the rest of them as mentors/family but that's about it from her direction. Certainly Cirno isn't in love with her or anyone else in this story. Byakuren, I think kagakujinya hit it right on, motherly love with a side order of pervert, but nothing really serious.
Loving all the Nue x Murasa in the background though, they're so cute.