My point: Ririha has romantic interests toward Yuzumori. I suppose seeing Yuzumori smiling moved something in her: she understands that “stoic Kaede”, the girl she calls by her first name - which suggests a level of intimacy that, despite she keeps it for herself, Ririha definitely feels - that same girl she likes has somebody whom she deems appealing enough to be wanting to spend time with them, somebody who makes her SMILE. (and, doesn't it irritate you when the girl you like is happy because of someone else?)
One thing I have to disagree with you on, is that I think she won't have romantic interest in Yuzu. From the way she's been presented she could also be something like a close friend she grew up with that she refused to see anymore. There's no real signs that she likes Yuzumori in any other way than that, and Yuzu could have just suddenly cut off contact with her making her spiteful.
My theory is that she was probably close only with Yuzu growing up (shy girl maybe?) and when Yuzumori stop hangging around with her she felt the need to get back at her by becoming friends with lots of other kids while Yuzumori was to be alone and sad. But when she sees Yuzu having fun with Mimika she gets angry because Yuzu is still enjoying herself and feels no need to become her friend again. That her plan backfired and Yuzumori isn't alone or sad.
I do also have to point out she is okay with getting in Yuzu's personal space and the fact with the names suggests deep friendship. Odd though that she hasn't stopped calling Yuzu by her first name if they don't talk anymore....
Well I dunno, maybe you're right and I'm reading things wrong. ┐(￣ヘ￣)┌
![[shibuya%20susano]%2062424338_p0](/system/images_images/000/006/754/medium/[Shibuya%20Susano]%2062424338_p0.jpg?1714750684)
