Any Iris/Bianca H-scenes? (Maybe Iris saving Bianca from a vampire and Bianca thanking her rescuer? ;) )
Also one benefit of adding this interaction is maybe having a scene later in the game where Mila mentions Iris to Bianca, and then Bianca is able to relate how she knew Iris, maybe even be able to deliver a message or something to Mila that Iris wanted her to know/have, since the two of them were so close.