I agree she isn't the type to get caught up in the moment I was just spit balling something that could explain it. > we saw her pass by her classmates without batting an eye so being rude is clearly not a concern to her
I assume what you're referring to is this page? I don't know about you but I do not consider this rude. If one of the the girls had say "Hey Yuzumori-chan" or something and she had continued to walk then yes that would be rude but I don't think you need to acknowledge people every time you walk by one another, especially when they're talking among themselves in fact if she said something to them she'd be interrupting their conversation, but I may be a rude person or it may be a Japanese thing I don't know. This is completely different to a situation when somebody goes to high-five you and you reject them.> I don't think those girls would be so friendly towards her had she not changed her attitude first.
The thing is we haven't seen enough of Yuzumori in school to really tell what is normal for her. Sure glasses-chan said she's by herself but just because you don't have friends doesn't mean you ignore people and don't respond to them, you can still have neutral relationships in my experience, and considering that children (in my experience) are nice I think the way these girls talked to Yuzumori is weird even if she hadn't changed her actions.
However I do agree that if those girls were in her old group of friends then it would be weird for them to act so friendly without Yuzumori changing, because she cut herself off from them which can be considered hostile (in my mind her relationship with those she wasn't friends with in the first place stayed the same, because there is no reason for it to have changed), but Ririha's group and Yuzumori's teammates are different people so I don't think this is an issue.
In any case talking about this is kinda fruitless because we have so little information about what was normal for Yuzumori.