His birth mother did not yet believe in Him?
Surely you can’t serious when you say this.
As for your interpretation meaning that Jesus’ words to the crowd might mean that He automatically excludes His mother; actually He is calling everyman to the level of faith and faith-living exemplified by His mother.
Of course, I fully understand that this is a YOPIOS situtation.
We have no way of knowing Mary's level of faith at all points of her life. We know only what the Scripture contains. Certainly there are times when it can be inferred that Mary experienced ups and downs in her faith, and at times one can infer she may not have understood the true nature of her Son. This is one of those times.
Mary did not understand the magnitude or the purpose or work or destiny of Christ . She, like most Jews was looking for a political Savior to free them, a new King.
Remember when Jesus chided her?
Luk 2:46 And it came to pass, that after three days they found him in the temple, sitting in the midst of the doctors, both hearing them, and asking them questions.
Luk 2:47 And all that heard him were astonished at his understanding and answers.
Luk 2:48 And when they saw him, they were amazed: and his mother said unto him, Son, why hast thou thus dealt with us? behold, thy father and I have sought thee sorrowing.
Luk 2:49 And he said unto them, How is it that ye sought me? wist ye not that I must be about my Father's business?