Friend of Marie Antoinette
She was described as a calm woman in which no situation, circumstance or object could shake.
She married to Comte Jules de Polignac, who had little money.
Marie Antoinette was touched by her sweet tender voice, and Mme de Polignac’s sensibility and constantly melted into tears. With her, Marie Antoinette did not feel she was a queen but herself. She need friendship for the emotion she could not get in her marriage.
Marie Antoinette helped Mme de Polignac as a friend by appointing her husband "reversioner" of the Comte de Tesse, her First Equerry, with horses, carriages, booming salary, etc. The public saw it as blind infatuation for the Comtesse de Polignac. However, the total amount of money Mme de Polignac spent in 14 years was less than Madame de Pompadour (Louis XV’s mistress before Mme du Barry) in one year.
There was no indication that Rosalie was Mme de Polignac’s daughter. But she had a twelve year old daughter whom she wanted to marry out to obtain more wealth and power. Her daughter married to Duc de Guiche at 13 and bore his first child at 14.
There was also no indication that she had several conspiracy including Marie Antoinette's fake pregnancy or killing the royal commander.