After researching for a bit, I've learned that the girl with the hair flower is an original character from a fan created anime. She is Sanae's older sister, Kochiya Yayoi.

https://anidb.net/perl-bin/animedb.pl?show=character&charid=91420

https://anidb.net/perl-bin/animedb.pl?show=anime&aid=12338

Edit 1: Should I tag this with incest + sisters or not since the character is not canon?

Edit 2: Derp, she already had a tag.

Ars said:

older sister

OOZ662 said:

My kinda-similar-but-not-worded-exactly-like-that thoughts too.