Mother Teresa loved her Sisters with all her heart, but she recognized that they had their faults, like all of us. She wrote to Archbishop Périer: "...I have to find the answer to the difficulty that sometimes comes from the Sisters' different characters, etc. Yet, Your Grace, how we have to thank God for our good Sisters - in spite of all their shortcomings they are very fervent and generous - God must be very pleased with the great amount of sacrifices these young Sisters make everyday. God keep them so."
She had to discipline and direct the Sisters in love to remind them that they must conform to the way of the Missionaries of Charity, to a life of service, sacrifice and sainthood.
I believe we can see God in Mother Teresa's understanding of her Sisters' frailties - that He loves us in the same way. He disciplines us in our sin, but He does so with a love that assures us that He wants what is best for us, that He wants to guide us in the way of holiness: "My (child), do not make light of the Lord's discipline, and do not lose heart when he rebukes you, because the Lord disciplines those he loves, and he punishes everyone he accepts as a (child)." (Hebrews 12:5b-6) If our hearts are open, we will recognize His chastisement: when our plans, which perhaps did not match His, go awry; when we read or hear something that convicts us in our hearts; when we come face-to-face with our own hypocrisy.
"Father, look not upon our sins but on the faith of your Church", we pray! God knows that we try our best, and though like a child we may balk at His forming us, deep inside we know His love is a constant in our lives.
Bl. Mother Teresa, pray for us!