Which is itself a non-biblical perspective. "Sola scriptura" is specifically rejected in the New Testament, and rejected by the "Portestant's substitute for Peter" (i.e. St. Paul).
"An argument that doesn't mean anything. Let's suppose for your sakes your statement is correct. What does it mean? Nothing other than Mary would be the first believer. That does not accord her any status other than she believed first. It does not make her the "mother of the church" much as you want it to be.
You Protestants make a big deal about "accepting Jesus" and "having a personal relationship" with same. Mary did both first, and was therefore, even by Protestant definition, the first Christian. I would think that simple logic would tell you that she is therefore deserving of a high level of respect from subsequent Christians.
Mary does not save anyone nor can she answer anyones prayer.
There are no other writings noted to be inspired by the Spirit outside of the Bible. Nothing else is needed for the believer in how to know God and believe.