(Possibly better suited on the Skeptics SE, but the claim is completely related to chess)
In 1922, she exceeded all expectations. Maria Theresa became the only woman to ever to have competed with men in the Cuban championship and won. After that, the only World competitions she entered were women only — first in Buenos Aires 1939 (coming in 7th), and in Moscow 1950 (winning 4 and drawing 4). She entered the Cuban Women’s Chess Championship which she dominated as winner from 1938 to 1960, when she retired. In 1950, Maria Theresa was named the first Latin American woman to be given the Women’s International Master title. When Capablanca and Maria Theresa finally competed against each other, it was a three game series. She won twice and had a draw for the third game. Nobody could have imagined the pupil would beat the teacher. In typical early 1900's fashion, she was remembered to have said “¡Ay qué pena, le he ganado!” (“oh how embarrassing, I’ve won”).
Considering that Maria Teresa finished well behind Vera Menchik in Buenos Aires 1939, and that Vera Menchik's record against Capablanca is 0-9, I find it hard to believe that Maria Teresa actually did beat Capablanca 2.5-0.5. There certainly is no record of these games in the Chessgames database.
Still, it's possible that the Chessgames database is incomplete, so I would like to confirm if the claim is indeed true (or untrue).
Edit: if the claim is true, I would very much like to see the moves in the games.
Edit #2: it seems the author of the source cannot verify the claim either, and has added a disclaimer to the bottom of the article.