When Sarah was added, it was the first time that Yuzu mentioned being in love with a girl/ being gay. Maybe Sarah will show her thatn being gay is ok...Because, this issue has to be adressed too. I mean the fact that they are both girls.
And Sara looks like a genuine person, so i think we shouldn't jumb on the conclusions about a new "love triangle" so fast...Like it was stated before many times, it is not s real triangle if Yuzu (or Mei) are not not really interested for the third person. Plus, Himeko and Matsuri haven't been so bad at the end, so I don't get what is so frustrating about new characters as I don't consider them a threat to the main couple.