What Mother Teresa did in her life is already much bigger then any miracle. “Miracles” are performed mostly by con artists.
This is why the Church insists on stringent investigation by medical experts who are not all Catholics (or even all theists) and who in practice reject most purported "miracles," only rarely certifying a cure as "medically inexplicable."
For instance, at the famous healing spring at Lourdes, France, there have been thousands of purported healing miracles since 1858, but only 68 of these thousands were investigated and found to be medically inexplicable. That would be somewhere around 1 - 2%.
Miracles are not meant to be a methodology of healing, in competition with the practice of medicine. (Thank God for doctors!) They're meant to be a sign. All these signs are worth --- in fact, demand ---- careful investigation.
I would go so far as to say a life lived in love and unselfish service is as great a miracle as raising the dead.