I think new addition has some potential, especially because she's interested in Shun. She always felt kinda of alone and disconnected, in contrast to Natsuki who has a lot of contact. So it feels like an opportunity for character growth on her side.
It's also an interesting twist to have a love rival who's aware of the relationship, although of course she's not going to have a lot of friends among the readers with a move like that. But yeah, for me, that's the kind of character with vibes that say "she needs a hug, and someone to show her a better path to follow in life".
