This appears to be her sister?
and that girl is not her sister because her sister is younger I think is the choreographer of new PV
It really is her sister. She wrote it herself on her blog.
友のお姉ちゃんニコニコドキドキなんてね~(笑)可愛いでしょ?大好きなまいかちゃん(ダンスの振り付け先生ドキドキ)今食欲と戦ってます(笑)Tomo.