Mother Teresa became famous by helping poor and everyone said to come and help her.
Mother became famous because she cooperated 100% with the Will of God for her, and you cannot help but make a visible difference when your partner in life is God!
The answer is not obvious to modern people as they did not understand Mother Theresa (as of 2013, she is Blessed Teresa of Calcutta, with another miracle, she will be St. Teresa of Calcutta) because they do not understand real Christianity. Blessed Theresa of Calcutta, a Catholic sister who entered the Sisters of Loretto in Ireland to become a teaching sister, was sent to India to teach. Later, moved with compassion, and the love of God, she received a "call" from God to help the poorest of the poor. The rest of her life was spent in "darkness" which I discuss below.
Modern people, and most people who call themselves Christians, think that going to Church on Sunday, saying some things, and being nice to people is what it is all about. They are completely missing the mark. Those kind of things are just the tip of the iceberg. Mother Teresa helped others by loving God above all things, putting Him first in her life, and doing His Will no matter how painful it was for her, and it was very painful.
Mother spent most of her life in a dark night with no real feeling or personal knowledge of God. This is very common with the founders of religious orders, they are strong enough in their faith to make their way through life totally depend on Faith, Hope, and Charity: the three cardinal virtues bestowed on us in Baptism. She sacrificed herself completely for God, and was called a saint and a prophet for it.
Mother Theresa helped others the way we are all called to help others, by getting up in the morning, and taking some time to give to God first. She spend an hour in Adoration before the Blessed Sacrament, went to Holy Mass, received Our Blessed Lord in the Eucharist, and went to confession frequently, and regularly. And, then, when she had done these things, she went out and lived her faith by seeing her God in every individual in front of her, especially the poor, the sick, the aged, and the abandoned. She served God by serving Him in them - which is nothing more nor less than she lived the Gospel with every breath in her body.
Mother Teresa showed compassion for those who were less fortunate than she was. She gave them food, lifted their spirits, and helped them survive. She is and was considered a hero to many people. After her death, she was put on the short list for canonization, and in 2012 I believe she has already had one miracle attributed to her, and has been beatified. Of course, she loved children.
The Church often says that the only real way to help people, the way to become a good spouse, parent, teacher, or whatever, is to become a saint. Mother Teresa believed and lived this. She helped the poor by becoming a saint.
The various ways that she accomplished that was that she always did the Will of God even when she didn't feel as if God was there or approving of her. She cared for the poorest of the poor.
She established hospices and hospitals for the sick and dying,
she started in Calcutta as she started a new religious order, the
Missionaries of Charity, which spread throughout the world. Today
the Order still cares for the poorest of the poor, the sick and
dying. Mother Theresa and her sisters went out into the streets and
picked up the dying homeless to bring them to her hospice. They
clean them, feed them, pray with them, and serve them so that they
spend their last days or hours in dignity. She and her Order treat
those dying of AIDS, the lepers, the untouchables, those whom
nobody else will love and care for. She saw Our Blessed Lord in
everyone of them, in disguise, pleading for our help and love. She
treated them as she would treat Our Blessed Lord,