Mother is a titled conferred on members of the Loreto Order when they become sisters. Mother Teresa originally wanted to take the name Therese after terese of Lisieux but that name was already taken by another member of the order. She chose instead to take the Spanish version of the name - Teresa.
Teresa was the name she chose upon becoming a nun. The title 'Mother' was a title given by the Sisters of Loreto to all nuns in the order.
Mother is the title given to the leader of a religious order - Mother Superior. Also, Mother Teresa was originally a Sister of Loreto, they are given the title Mother (as opposed to Sister) as soon as they make their final vows, so Mother Teresa was known as Mother even as a teaching Sister.
No, the title 'Blessed' was given her when she was beatified.
Mother Teresa
No, the proper title is the Missionaries of Charity. Informally, I suppose, Missionaries of Mother Teresa would be okay.
In March of 1997 she relinquished the administrative duties to Sister Nirmala who had been elected to be the successor to Mother Teresa. Mother Teresa remained as the Mother Superior of the Order until her death when the title passed to Sister Nirmala. In other words, Mother Teresa went into partial retirement.
It is traditional for religious to take a new name when they join a religious order. In the Sisters of Loreto, when a woman makes her final vows, she take the title of Mother. Mother Teresa took the name Teresa in honor of St. Therese of Lisieux, a patron saint of missionaries.
She has been beatified by the Catholic Church and the title that goes along with that honor is 'Blessed.'
Mother Teresa to have them.
Mother Teresa did not participate in or follow sports.
Nirmala is the name of the successor of Mother Teresa, not the name of Mother Teresa.
She has been in the process almost since the day she died. Right now she has the title of Blessed Mother Teresa of Calcutta and it is only a matter of time before she is declared a saint.