I would NOT detach her from Francis Brown.
Clearly Francis Browne married a Mary Johnson at Newbury and had the children listed. After her death, Francis supposedly remarried and had Benjamin. I haven't found a notation that clearly states the parents of Mary Johnson Browne in a very brief search.
Maybe you should detach this Mary Johnson from the listed parents, if you can confirm that their daughter is the Mary Johnson that married Ephraim Davis?
From: Vital Records of Newbury Massachusetts to the End of the Year 1849:
(p. 263) Johnson, Mary, and Francis Browne, Nov. 21, 1653.
Newbury Births: BROWN
Benjamin, s. [Francis. S. dup], Apr. 20, 1681. (p. 66) (? by 2nd wife)
Francis, s. Francis, Mar. 17, 1673.
Hanna, d. Francis, Oct. 19, 1659. (p. 67)
Elizabeth, d. Francis, Oct. 17, 1654. [Jan. 26. S. dup] (p. 73)
John, s. Francis, Mar. 13, 1664[-5. S. dup] (p. 74)
Joseph, s. Francis, Sept. 28, 1670. (p. 74)
Mary, d. Francis, Apr. 15, 1657. (p. 74)
Sara, d. Francis, May 10, 1663. (p. 74)
Thomas, s. Francis, July 1, 1667. (p. 74)
BROWNE, Mary, w. Francis, Apr. 4, 1679. (p. 555)