It is a blessing (although Olga would have been out of the country at the time of the revolution) that Olga didn't take Prince Carol. Having read biographies of the Roumanian royal family and seeing Carol's thoroughly bad behavior to his mother and to his wives, I think Olga would have been miserable.
Of course, she would have had Missy for a mother in law, so maybe things wouldn't have been as bad for Olga as they were for Missy when she first arrived in Roumania as a young bride.