The author does a good job keeping the characters consistent so far. Tomiko's distrustful because she knows how quickly people tend to turn on one another and so she doesn't trust anyone. She's not necessarily being invective towards Kanae, hell, she may even be trying to help her, but her blunt way of saying things and her distrust of people makes it seem like she's attacking people when she's really trying to be protective of people close to her, even if it comes across as rude.
Kanae puts all of her self-worth and value into Hiroshi, and has deified him, so when Tomiko begins to question his motives in the hopes of trying to help Kanae, obviously she'll flip out at her. Tomiko obviously doesn't view Kanae in the best of lights because of Ichika's sudden disappearance, but she's not attacking her out of a sense of jealousy as much as how she addresses her is in the same way she's always been treated by the ingroup, so doesn't quite understand where she's going wrong.
It's interesting as a dynamic, and I like who the character who we're lead to believe is the ugliest both internally and externally is revealed to be one of the most nuanced in the entire manga