I think that The Emperor has to approve the right of husband of Yussupov's girl to take the family name.
Only Tsar . But it is in Russia.
Maybe in Europe , it is more simple.
As for her life in exile, I found the following item:
it seems that she said" the trials which were sent to us- they are for our sins".
As far as she had the money and energy, she helped Russians in Roma. She made in Roma Job Bureau , free
trattoria for russian people who went abroad without any money. She also opened an atelier where the underwear were made. She sent it to the poor Russians.
So she accepted her new position but not only accepted such misery position, but also tried to help others to find new way of living.
After her husband's death , she came to Paris to be closer to the son and to the grand daughter. And then, she died on 1939.