Mother and son in Buenos-Aires.Lennart visited Maria Pavlovna in Argentina

According to
Flight of the Romanovs by Perry and Pleshakov @ p 339-40:
... Marie Pavlovna saw her son in Buenos Aires in 1947, when Prince Lennart travelled there on business. According to the authors it was the first time they had an adult conversation, where she apparently confessed her personal loneliness and not having a real 'home'.
In later years she found difficulty relating to her grandchildren. Her only true affections were always for her brother Dmitri.
She died a sad and lonely woman, never able to relate to anyone else, despite her considerable artistic talents.