I deny that I have a promise that Mary can hear anything I say.
If I ask my cousin to pray for me, but he's in another state and I didn't use the telephone, then I'm pretty sure he didn't hear me and my prayer request was useless. However, if I ask him in person or on the telephone to pray for me, and he says he will pray for me, then I'm pretty sure he heard me and I didn't waste my time.
Wishful thinking and conjecture are foolish ways to practice religion.
If millions of Catholics are praying to Mary at the same time and she can hear all of them, you are giving her the attribute of omnipresence.
You need a promise?
What is faith?
Perhaps you would do well to learn about the process for canonization of Saints?
It requires that 2 documented miracles be attributed to having asked the “saint” to ask Christ for help in a certain matter.
It is a very strict process that begins with extreme skepticism.
Did not Moses and Elijah appear with Christ in front of Peter?
Why do you believe they are unaware of anything on earth?