Er Niang wouldn't be destitute living with the Xus, but she wouldn't be happy there either. And she definitely woundn't have remained in their manor nearly as long as Shiyi.
Think about it. There is no way she would have gotten control over the Xu household. Old Madame adored Lady Qiao and although she was officially a concubine, everything would have stayed in her hands.
Er Niang, which she refuses to remember, is only a concubine's daughter -- illegitimate, and a stupid and selfish one at that from a family with no clout (the Luos).
Lingyi would have thought as little of her as he did all the others. Maybe even less because she never would have overcome his suspicion of her scheming with his late wife.
She would have been killed with no one caring to investigate.
Shiyi, on the other hand, wouldn't have been bothered by her husband, Duke Wang. She used her brother-in-law's might and influence when she encountered him her first day in the city. Like he suddenly became "nice" to Er Niang after Lingyi threatened him, he would have been that way towards Shiyi from the onset. And fortunately for Shiyi, he always had outside interests to keep his pants occupied. As far as raping her maid, does anyone think Dong Qing couldn't handle his drunk ass?
Because of her capabilities, Duke Mao would have respected Shiyi more than he did his son. Therefore, she would have been treated better in their household than Old Mme Xu tried to treat her.
