Catholics ask Mary to pray for them. IIRC the Bible tells us to pray to the saints. Surely Mary is a saint. I would love to know that Mary was praying for me. That does not mean that I would be worshipping her.
You ask, and receive not; because you ask amiss(James 4:3)
You do know, however, that all saints are seeing us and praying for us:
And therefore we also having so great a cloud of witnesses over our head, laying aside every weight and sin which surrounds us, let us run by patience to the fight proposed to us: Looking on Jesus, the author and finisher of faith, who having joy set before him, endured the cross, despising the shame, and now sitteth on the right hand of the throne of God. (Hebrews 12:1-2)another angel came, and stood before the altar, having a golden censer; and there was given to him much incense, that he should offer of the prayers of all saints upon the golden altar, which is before the throne of God. And the smoke of the incense of the prayers of the saints ascended up before God from the hand of the angel. (Apocalypse/Revelation 8:3-4)
Prayer is offered to God, never to any created thing. To do so is to offer worship that should only be directed to God, which is idolatry.
Asking those dead for advice or intercession is the sin of Saul.