Our issue, I think, is that Jesus lives and Mary, just like every other person who ever lived, is dead. Nothing in Scripture supports praying to dead people - in fact, precisely the opposite.
Mary could very well indeed be dead but what about the Transfiguration with Abraham and Moses? Moses died but his body was nowhere to be found. Enoch was translated. Apparently some people are in Heaven for a purpose but the rest are "asleep".