I have estimated Marie's birth year. She arrived at Plymouth, MA, aboard the ship "Anne" in 1623. She may have come in the care of Elizabeth Warren who came with her five daughters (see Sould Kindred article mentioned below).
Her name is sometimes given as Mary Becket or Mary Bucket.
The earliest written record in Plymouth gives her name as Marie Buckett. She is next mentioned in the May 1627 Division of Cattle, listing George Sowle, Mary Sowle, and Zakariah Sowle. They are included in the section "Richard Warren and his companie Joyned with him."
"When she first set foot in Plymouth Colony in 1623, she was known as Marie Bucquet. In later records she was Mary. She was probably about 18 years of age in 1623 in order to travel by herself. If she was about 47 years old at the birth of her last child, she would have been born no later than about 1604." (source: The Mayflower Quarterly, Dec 2012, p 378, article by Louise Walsh Throop, MBA)
Soule Kindred Newsletter, Summer 2016, "Mary Beckett -- found?" article by March Kelly:
Latest research suggests that George's wife was Mary Beckett from Watford, Hertfordshire, England. Her grandfather was John Beckett, a tailor, who married Mary c1577. His will dated 20 July 1590 mentions son John Jr. and daughter Mary. John Jr. married Ann Aldyn in 1603 and they had five known children, including Mary in 1605.
[S013269] Edited by Anne Borden Harding, Mayflower Families Through Five Generations, Vol. 3, George Soule, (General Society of Mayflower Descendants, 1980), 3.
[S013963] "Possible English Origins of Mary Beckett" by Marcy Kelly Brubaker, Soule Kindred Newsletter, Vol XXXXVII No 4, Fall 2013.