The Hebrew word Elohim is Plural as The Elohim of Father, Son and Holy Spirit which is the Elohim God.
Let Us God, is plural.

Quote
And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creeps on the earth.
Genesis 1:26
Only God made anything the "Us"..
All things were made by him; and without him was not any thing made that was made.
John 1:3

Let us make = made.
It was the Elohim God referred to Himself in the plural.
Mary is not in that quotation at all.
She was blessed but very human.