Empress Dowager/Spoilers

History
She has known Bai Ruo Qi since she was a young girl and thinks highly of her.

Peach Blossom Banquet
This completely screws up Bai Ruo Qi's plan so she throws the Court Doctor Liu under the bus in front of the Empress Dowager. Empress Shu - who was there for the fun of watching Bai Ruo Li fall from grace - assists Bai Ruo Qi and almost gets Doctor Liu thrown in jail. Bai Ruo Li asks the Empress Dowager to get to the bottom of this and thus Bai Ruo Li is able to interrogate Doctor Liu. He retaliates for being discarded by revealing that every time Bai Ruo Li was invited to the palace, the Bai family would get medicine from him to make Huang Yue Li sick. He also divulges that he supplied medicine so that Bai Ruo Qi could have her raped by an extremely ugly young man.

After the Peach Blossom Viewing, her support of Bai Ruo Qi is completely dashed and instead favors Bai Ruo Li in the subsequent conversation (with the Imperial Empress, Emperor, and Imperial Tutor) on who should be engaged to the Crown Prince.