Okay, this is how I’m figuring out 方…
Page 59 - 追いかけてくる方が？- the one (sister) who chased me?
Page 59 - つよい方か？ - the stonger one?
Page 59 - そっちじゃない方だ - not that one.
Page 59 - きれいじゃない方か - the one who’s not cute?
Page 70 - のきれいじゃない方だ - the one who’s not cute!
方 = one
It works for me, is it correct?