Mary makes requests on our behalf. She made a request for others when Jesus performed the miracle of Cana, she told Jesus they were out of wine. Even though Jesus told her His time had not yet come, she did not withdraw her request, she made it clear she would accept whatever response Jesus gave. Asking those in Heaven to pray for us is an old practice, going back as far as Psalm 103. I know many Christians have dropped the practice, that is their choice. Of course a personal relationship with Jesus is at the heart of Catholicism and I do make prayer requests directly to Jesus, but Holy Scripture tells us to pray for one another and I take the Word of God seriously.