I firmly believe that the Immaculate Conception of Our Lady, but I wonder did she ever commit a sin, venial sin included. I know some Greek Fathers said Our Lady sinned during finding Jesus in the temple and during the Passion of Jesus. What is the opinion of Church?
It is the belief of the Catholic Church that Mary was free from both original sin and from all personal sins. It is especially borne out in the dogma of her assumption, as the sinless Virgin Mary’s body did not experience corruption.
This is not because she was not free to sin. On the contrary, being uniquely free of original sin at conception, she was more free than any of us. Rather, she humbly exercise all her freedom in throwing herself lovingly and wholeheartedly into following God’s Will.