Maybe it comes down to it being slightly underestimated quite how much Rinny likes the MC? I haven't had the chance to check out the yandere content yet (I'm definitely going to!), and I could be wrong but I personally came to the conclusion that Rinny legitimately loves the MC, and that's why it was also a bit easier for her to come to her decisions. Thus, I was able to forgive her more easily with this in mind, especially with her honestly believing the MC would be happier that way.