Wife of Gayen Miller, member of Kennett MM and records for family can be found in Newark MM book.
List of children of Gayen & Margaret comes from that as follows:
James B: Nov 5, 1696 D: 1732 M: Rachel Fredd
William B: Aug 30, 1698 D: 1767? M: Ruth Rowland
ROBERT B: Mar 3, 1703 D:1761 M: Ruth Haines
Sarah B: Sept 1, 1704 D: 1749 M: Joshua Johnson
Mary B: Feb 7, 1707 M: William Beverly
Patrick B: Dec 28, 1708 D: 1751 M: Patience Haines
Samuel B: Apr 14, 1711 D: 1764 M: Margaret Halliday
Elizabeth B: May 7, 1713 M: Joseph Dickinson
Joseph B: Jul 14, 1715 D: 1742 M: Jane Kirk
Benjamin B: Jun 4, 1717 M: Martha Walter
John B: Nov 6, 1720/21 (provision of old style to new)
M: Margaret Smith
George B: Aug 19, 1723 M: Susanna Bird

OS dating applies to her memorial. Dates for her are all over the place.
Trees on Ancestry have her birth year as 1674, but have attached a record for birth of 1681....
the following marriage records can be found:

Name: Margaret Henderson
Gender: Female
Birth Place: Ir
Birth Year: 1667
Spouse Name: Gayen Miller
Spouse Birth Place: Ir
Spouse Birth Year: 1664
Marriage Year: 1695
Marriage State: PA
Number Pages: 1
--- and -----

Name: Margaret Henderson
Gender: Female
Spouse Name: Gayen Miller
Spouse Birth Place: of PA
Marriage Year: 1695
Number Pages: 2

WILL
Margaret Miller of Kennett. Widow of Gayen. January 11, 1743/4. January 26, 1743/4. B. 152. To son George Miller all estate except as other wise devised. To granddaughters Margaret Dickenson and Margaret daughter of William Miller articles named. To sons Patrick, Benjamin and John Miller and Joseph Dickenson £5 each. Executor: son George. Witnesses: Stephen White, Mary Jackson, Jos. McDowell.

Contributor Gerilynn M Campbell (47834227) sharing the following:
Margaret was the daughter of Scottish Immigrant Parents who moved from Scotland to Northern Ireland for a short time before coming to America. Her parents were Patrick Henderson and Barbara Forrest. She was born in Haddington, East Lothian Scotland, on 29 Apr 1681 and was baptized in that place on 01 May 1681. She was in her 15th yr of age when she married Guyon Miller, an Irish immigrant.