A few interesting things were brought to my attention, Korekore mentioned that they met up in November and I decided to archive search what I could find and here is were we can start a timeline. So the first major thing is Rushia's hamster died which is rather sad so if MafuMafu decided to comfort her this could have led to her developing feelings. Now the first concrete date of interest is November 11th where Rushia under her roommate simply tweeted she was "sorry" without specifics this could mean a number of things given what we know either this is when she confessed or the actually got together. The next date is the 13th where Rushia seemed to have a breakdown on stream people at first thought she was getting messages from her manager and assumed they canceled something like they did to Pekora though later Rushia herself said it was because of all the long neck comments but given the new context it could have possibly been MafuMafu. Now for the biggest potential rrat on November 14th there was a minor yab (at the time) about someone claiming to be Rushia's ex posting proof that she was currently dating someone, the wayback machine doesn't want to work for me and the images will only occasional load but link here
https://web.archive.org/web/20211114224357/https://twitter.com/mylife8752/
>今とても大切な彼氏がいて
>そして俺はぺこみこ推しだから本人には女性として全く興味はない
it also mentions this account https://twitter.com/akismxx who yesterday was trying to get on skype with Korekore to air is previous involvement with Rushia. This all paints an interesting picture