Her peers didn’t agree that she was sinless.
First of all, Mary has no “peers”. She occupies a role in salvation history that was not, and will not, be occupied by anyone. Are you suggesting that the other Apostles ought to have accused her of sin?
27And it came to pass, as he spoke these things, a certain woman from the crowd, lifting up her voice, said to him: Blessed is the womb that bore thee, and the paps that gave thee suck. 28But he said: Yea rather, blessed are they who hear the word of God, and keep it.Luke 11
Jesus affirms that Mary, though she knew she would be called “blessed” in every generation by the privilege of bearing the Christ, was even more blessed because she heard the word of God, and kept it. Just as Jesus cleansed His Apostles by His Word, He cleansed His mother.
The Apostles didn’t say, they knew she was sinless
It is true that Luke was not an Apostle. His deliberate arrangement of the birth narrative to demonstrate that Mary is the Ark of the Covenant is usually lost on evangelicals. The early church understood that Mary was the new Eve.
You claim Mary is sinless without confirmation from the word of God.
I think you have not read about the meaning of κεχαριτωμένη
“kecharitomene.”
“chaire” - Means "hail” or “rejoice”
“charis” – Means “grace”
“charitoo” – Greek verb ending in omicron omega (“oo”) means to put the person or thing into the state indicated by the root. The root being “charis” or “grace,” “charitoo” means “to put into a state of "grace.”
“ke” – Greek perfect tense prefix indicates a perfected, completed present state as a result of past action. Thus, a perfected, completed present state of “charis,” or “grace,” as a result of past action.
“mene” – Greek passive participle suffix indicates action performed on subject by another. Thus, a perfected, completed present state of “charis,” or “grace,” as a result of the past action of another. As the speaker is the angel Gabriel, the “other” is God.
Therefore, “chaire kecharitomene” means: “Hail, who has been perfectly and completely graced by God.”
κεχαριτωμένη indicates that Mary was placed into a perfect state of grace (free from sin) prior to the visit of the Angel. Gabriel greeted her as κεχαριτωμένη, used as a title, rather than her name.