Why do you need scriptures to tell you that asking other Christians to pray for you is a good thing? Praying is not a solitary thing- it is something that makes us part of a greater Christian community. By praying with Mary and asking her to intercede on our behalf, you don't really do anything different than when a congregation prays on behalf of a sick person, for example.
Mary can't hear you because Mary is not OMnisicient (that quality applies to God only) and that is what is required to hear the billions of prayers all at once.
And I say again, you are using a mediator and that goes against scripture! Deal with that. The bible says that Christ is the ONLY mediator. Get that thru your head. It also says to come boldly to the throne of God not boldly to Mary.