Disobedience to God is the basis of sin, so could Mary, who by her Immaculate Conception was made to be unable to sin, really have been able to say no?
The following links should assist you in better understanding Mary’s role in salvation history. If you have any further questions or concerns that are not answered by these links, please [contact Catholic Answers (http://www.catholic.com/home/contact.asp) directly.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.