.The Bible DOES speak to the issue of Mary.
IT DOES NOT however even suggest that she was sinless.
Luke 1:28, "kecharitomene", properly translated "full of grace", suggests sinlessness, although you are correct that it is a matter of interpretation rather than direct scripture.
Let me ask you this: Why is it so important to you to insist on Mary being a sinner and also having marital relations with Joseph? Is it because the Catholic Church teaches otherwise, or is there something in your personal understanding to Christianity that does not square with the notion of sinless and ever virgin Mary?