How do you know that Mary or any other human that has gone to Heaven can hear your prayer? If millions of people on Earth are asking her to pray for them, can she hear them all? If so, wouldn’t that require her to be omnipotent or omnipresent?
Is the body of Christ separated? Does your leg need to hear your arm to be part of one body? Does one part of your body become ill while the other is healthy? Can you have compassion without words?
Do you say the creed: "I believe in the Communion of Saints"?