You omitted important context, read the whole thing:

26 When Jesus therefore saw his mother, and the disciple standing by, whom he loved, he saith unto his mother, Woman, behold thy son!

27 Then saith he to the disciple, Behold thy mother! And from that hour that disciple took her unto his own home.

He was speaking directly to him, not to us. And even if He were speaking to us, no where does that scripture suggest we must pray to Mary instead of Jesus, God, or the Holy Spirit.