It is not that Rong Rong is someone special and they all thought only good about her. It is just that she always spent all her time with all of them while learning about acting from them. If she really wanted to act like a stuck up then there is no way that she would have any contact with any of them before this too.
Since she had the support of Sun Bingwen, no one would dare say anything to her even if she acted stuck up but she did not. Hence they all subconsciously sided with her in their minds.
When Rong Rong went to Sun Bingwen's room, everyone congratulated her while the room was filled with Sis Xiao's enthusiasm for her sister's success.
Within some time, Rong Rong's script arrived and everyone gave her some time so she could read everything clearly as there was not much time left.
When Shao Rong saw her first ever scene, her pupils immediately contracted. Is this really a coincidence or is it a premeditated plan?