For Mary, conceived without the stain of Adam, original sin. For everyone else, through baptism and the sacrament of penance.
Nonsense. Every human with the exception of Adam, Eve and Christ Himself was conceived in sin.
This is why Mary needed grace just as every human does. She herself in Luke 2 called God her Savior because she humbly knew that she also was in a sinful condition and needed salvation from it.