1. Prayer means several things - "I then prayed my friend that he would accompany me on my trip to Italy" does not mean that you worshiped your friend. Mary (and all the saints) are prayed to in that intercessory way, not in the worshipful way that we pray to God. The man at the Beautiful Gate asked Peter for charity and Peter gave him the ability to walk, not by his own power by by the power of Jesus (Acts 3:2-6). And again intercessory prayer as an important part of the life of the Church is well-attested - e. g., St. Paul in 1 Timothy 2:5 says "I urge that supplications, prayers, intercessions, and thanksgivings be made for all men". Finally, why the focus on Mary above all other saints? "Who am I, that the mother of my Lord should come to me" says Elizabeth "filled with the Holy Spirit" and before that "Hail, full of grace, the Lord is with you" says Gabriel bringing God's message to Mary. And what does Mary say in response? "My soul magnifies the Lord, and my spirit rejoices in God my savior" and "I am the handmaid of the Lord, let it be done to me as you have said". When trying to draw closer to Christ, who would you want with you on your journey more than she who was called to be His mother? And who among all mankind would be more eager to have you come to the throne than she for whom "the Almighty has done [great things for]"?

2. "In fact, [God has not forbidden contact with the dead], because he at times has given it — for example, when he had Moses and Elijah appear with Christ to the disciples on the Mount of Transfiguration (Matt. 17:3). What God has forbidden is the necromantic practice of conjuring up spirits. " Via https://www.catholic.com/tract/praying-to-the-saints