"I have a few questions. If Mary was sinless, then everything she spoke, thought, and did was without sin. If she spoke without sin, then nothing she said was erroneous. Do you agree? Would this mean that she was considered to have always spoken truth?"
Mary would not have lied, but that doesn't mean she was omniscient. She was/is a human being and therefore her intellect would have been subject to ignorance like ours during her earthly life.
As to your questions about her parents, Stubborn has given some excellent answers to these in #122.
"Can someone live a sinless life without being a diety?"
Its not common, but Scripture does attest to this:
Lk 1,5 "In the days of Herod, King of Judea, there was a priest named Zechariah of the priestly division of Abijah; his wife was from the daughters of Aaron, and her name was Elizabeth. 6. Both were RIGHTEOUS IN THE EYES OF GOD, OBSERVING ALL THE COMMANDMENTS AND ORDINANCES OF THE LORD BLAMELESSLY."
There is also the case of St. John the Baptist who was sanctified from the womb:
Lk 1,15 "for he will be great in the sight of the Lord. He will drink neither wine nor strong drink. HE WILL BE FILLED WITH THE HOLY SPIRIT EVEN FROM HIS MOTHER'S WOMB, and he will turn many of the children of Israel to the Lord their God."
From another post...
***This statement must be capable of admitting exceptions, because we see his disciple/secretary St. Luke asserting the following: Both were RIGHTEOUS IN THE EYES OF GOD, OBSERVING ALL THE COMMANDMENTS AND ORDINANCES OF THE LORD BLAMELESSLY." ***
But it is clear from the context that Luke doesn't mean they were "sinless" and therefore exempt from the passage in Romans because immediately he recounts the story of Zechariah's unbelief...
"And Zechariah said to the angel, "How shall I know this? For I am an old man, and my wife is advanced in years." And the angel answered him, "I am Gabriel, who stands in the presence of God, and I was sent to speak to you and to bring you this good news. And behold, you will be silent and unable to speak until the day that these things take place, because you did not believe my words, which will be fulfilled in their time."
Luke 1:18-20
Zechariah was clearly punished because he "did not believe". He did something wrong and got rebuked for it by the angel. Lack of faith is a sin as Paul says here...
Romans 14:22
... For whatever does not proceed from faith is sin.
***If you want a precedent of a Saint who was sanctified from the womb...HE WILL BE FILLED WITH THE HOLY SPIRIT EVEN FROM HIS MOTHER'S WOMB,***
Truly he was filled with the Holy Spirit from the womb, and Jesus calls him the greatest of all those born of woman, but this didn't render him "sinless". If John were "sinless" then why would he appeal to Jesus...
"Then Jesus came from Galilee to the Jordan to John, to be baptized by him. John would have prevented him, saying, "I need to be baptized by you, and do you come to me?""
Matt - 3:13-15
He recognized that he need to be baptized by Jesus.
Was Mary sinless? Here is a scripture below that might suggest otherwise:
Luke 2:46-49
46 Then, after three days they found Him in the temple, sitting in the midst of the teachers, both listening to them and asking them questions. 47 And all who heard Him were amazed at His understanding and His answers. 48 When they saw Him, they were astonished; and His mother said to Him, "Son, why have You treated us this way? Behold, Your father and I have been anxiously looking for You." 49 And He said to them, "Why is it that you were looking for Me? Did you not know that I had to be in My Father's house?"
The way I read this scripture, Mary is either offended by Christ or reprimanding Him for not telling His parents where He was going. So either Christ sinned (which we know is impossible) by not telling His parents, or Mary wrongly scolded her son (V.48).
How do you read and interpret these verses? Do you agree with my assertion?