I thought Qingyan doesn't like her sister all that much, but they seem just fine during the photoshoot.
Also, what is going on? They followed Qingyan's first suggestion, so why was Qingyan unhappy about it? And what does her hand gesture mean?
Also, does Qingyan wear a glove or something? It's all a bit odd.
As pointed out, Qingyan suggested "put your head on her shoulder." and Ren did that, at which point Qingyan said "NO, NO, other way around!" and since Youji is the taller of the two, it involved picking Ren up in an embrace, to Youzi's absolute glee.
As for the line on her wrist, nah, I think the artist just carelessly inked some of the structural guidelines they used to construct the hand while sketching.