She heard Xie Yu's confession, so she knows that the Chiyan army was framed by Xia Jiang. And therefore, she wants to rescue Wei Zheng because he was a brother-in-arms to her husband.

She's ready to take on a severe punishment (I think at some point she says she can take anything, even exile?), but the plan is strategic pleading on Consort Jing and Prince Jing's sides will save her.