Thanks. However, you should answer the question if you wish to truly understand the Catholic position.
But, asking Mary to 'pray for us sinners' is asking her to speak to God on your behalf.
Are you not essentially doing the same thing when you ask a living person to pray for you?
Not a single mention in the Bible about needing anyone to speak to God for you.
Needing is the wrong verb. Do you need other living people to pray for you? No, but Protestants ask them anyway. Moreover, it is not true that their in no mention of the communion of saints in heaven and their petitions to God. The Book of Maccabees, which Martin Luther conveniently excised from the Bible, makes reference to it, and so does the Book of Revelation.
Why did Moses blow his top upon finding his followers praying to an idol they had built, while he was atop the mountain? Are not little ceramic dolls, assigned the names of Saints & Mary, the very same thing?
No, they are images to assist the faithful to be mindful of a saint or of God. These images are not worshipped. Moreover, while Protestant do not like to see a distinction between veneration and worship, for Catholics the two are very different. Saints are venerated, held in great respect because of their fidelity to God. They are respected for their love of God--not as a god, thus the first commandment is not broken. Their veneration would be the equivalent of the love and respect you give to a great Protestant leader. If you still respect them after they are dead, you are doing essentially what Catholics do with saints, save that you are not allowed to ask them to pray for, despite the fact that you could when they were alive. God alone is worshipped because he is recognized as the source of all that is good.
People, by the way, who were made Saints only by the Catholic church, not God. He sanctioned their Sainthood's in no form or fashion. Unless you're speaking to the Pope, of course, then you will get the opposite of that truth.
Common usage aside, Saints are not made by the Church. The sainthood conferred upon a departed soul is merely an act of recognizing with a sense of surety of the salvation of an extremely pious individual. Catholics believe that soul is, indeed, in heaven. Thus God sanctioned their holiness, their state of salvation; the Church simply recognizes it.