We don't give her such attributes. Only Christ can forgive sin or prevent us from sinning; only through the grace of Christ we may be saved. It is only through Christ that the saints can intercede. It is through Christ that Mary has her glory and queenship.
That Mary was sinless follows from the description "full of grace" the Archangel gave her (Luke 1:28). It is scriptural. Nor is she the only one thus described; Noah as well is described as "just and perfect man" (Genesis 6:9), that is, free from sin.
If you read Romans 3:23 (your likely prooftext for the sinfulness of Mary) in its context it is clear that St. Paul writes in generalities. For example, he also says that "none seeketh God", but that clearly is not true of every one.
An appropriate quote for this thread.....
“All true children of God have God for their father and Mary for their mother; anyone who does not have Mary for his mother, does not have God for his father. This is why the reprobate, such as heretics and schismatics, who hate, despise or ignore the Blessed Virgin, do not have God for their father though they arrogantly claim they have, because they do not have Mary for their mother. Indeed if they had her for their mother they would love and honour her as good and true children naturally love and honour the mother who gave them life.”-Saint Louis Marie de Montfort
So Christ wasn’t the only sinless human you say? Really?