I think this proves that Iris is growing. She was always firm when presenting her ideas, but that battle with the church really damaged her mentally. It is awesome to see her growth without changing how she really is. Some authors give their main character growth in exchange for a scene that...
I like this development. It reminds me of a oneshot i read some time ago about a spirit being in love with the crush of the protagonist that also had the ability to see spirits.
crazy theory:
Kobachi Osaragi is dating tsubame senpai or at least experimenting. i ain´t got no prove is just because kobachi is apparently experimented in relationships and tsubame doesn´t want anything tying her down so maybe she be up for some experimenting. That smile at the end of chapter...