Do Catholics “pray to Mary”. Yes and no. Because we are “surrounded by a vast cloud of witnesses” it is best to say we pray “with” the saints. They are our prayer partners, and as the Blessed Virgin Mary is the Queen of that army of prayer warriors she is the primary saint with whom we pray.
We have to remember who Mary is. Mary is a totally unique person. She is the one human being chosen to offer her flesh to be taken by the Son of God. No other human being has this intimate relationship with God–that he entered her womb, took her flesh and was as close to her as any son could be to a mother. The church has rightly recognized therefore that she is “higher than the cherubim, more glorious than the seraphim”. If we pray with the saints we pray most gloriously and powerfully with her.
In addition to this, while we pray with the saints, we also ask us to pray for us–just as we would any prayer partner or prayer warrior. We know old Mrs Smith in the church is a great prayer warrior, so we ask her to pray for us. It’s a natural part of our relationship with the saints of God.
So, no, we don’t pray to Mary. We pray with Mary.
However, there is a sense in which we do “pray to Mary.” We don’t pray to her as we would pray to God. To understand what Catholics mean when we say that we “pray to Mary” we have to understand the word “pray” in a different sense. In this sense we are using the word “pray” in an archaic sense. In Shakespearian plays a character might say, “I pray thee good sirrah, lend me a ducat.” He is using the word “pray” to mean “ask” or “request”. Therefore when we “pray” to Mary we are asking her to pray for us and with us. This is expressed most clearly in the most famous and heavily used Marian prayer–the rosary.
So we say, “Hail Mary, full of grace, the Lord is with you. Blessed are you among women and blessed is the fruit of your womb–Jesus. Holy Mary, Mother of God, pray for us now and in the hour of our death. AMEN” We are “praying” to Mary, but the prayer itself is simply a request that she pray for us.
Do Catholics honor Mary too much: Here is an article from the Archived Articles section of the blog: Distorted Devotions–which goes into the question in more detail.