The term used for Mary is kecharitomene!, meaning "one who's always been filled with grace."
I was asked where in Scripture the Catholic Church has interpreted Mary as being born without Original Sin. I'm pointing out where.
I checked out the website and it does a poor job on the translation.
The phrase in question in Luke,κεχαριτωμένη, is a perfect participle middle/passive participle. We translate this as we would a perfect verb. The perfect denotes an action completed in the past with results felt in the present. But, the viewpoint is from the writer....not the reader.
The section in question, Χαῖρε κεχαριτωμένη is correctly translated as, "Greetings, you favored with grace."
To keep this in context, Luke was writing about an event that had already occured. From Luke's viewpoint Mary had already been favored with grace at the time of the announcment by Gabriel. The impact of which was still being felt at the time of his writing. We continue to call Mary blessed as a result.
It does not mean that at her birth Mary had been favored with grace. The text does not support this and the catholic encyclopedia online concurs.
As an example of this let's look at Luke 1:27 and the word betrothed. (ἐμνηστευμένην). It too is a perfect participle middle/passive.
Does it mean from Mary's birth she was always bethrothed to Joseph? Of course not. It simply means from Luke's perspective, remember, he's the writer, Mary was engaged to Joseph.
We also know from Luke that Mary also identified Jesus as her Savior. If she were sinless she would not need a Savior. To compare, we never saw Jesus offering a sacrifice as He was the sacrifice.
We also have Romans 3:23 indicating that all have sinned and fall short of the glory of God.
No where, repeat, no where, do we have the Bible noting an exception for Mary being sinless. No where.
There has only been one sinless person and that is Jesus Christ.
Luke 2:48 When his parents saw him, they were astonished. His mother said to him, "Son, why have you treated us like this? Your father and I have been anxiously searching for you."
Sin right there.