There was an Elizabeth Stedman born to Robert and Elizabeth Stedman on 5 Dec 1719, from LDS Vital Records for Charing, Kent, FHL Film  924129, but this looks a bit early for a marriage in 1756.
Or, a bit further afield, there was an Elizabeth Stedman born to William and Elizabeth Stedman and christened on 14 Feb 1723 in Hastings, Sussex but this is a bit early too.
Or, there was this baptism recorded on a more likely date, making her 20 at marriage:

First name(s) Elizabeth
Last name Stedman
Gender Female
Birth year 1736
Birth place -
Baptism year 1736
Baptism date 25 Jan 1736
Place Ardingly
County Sussex
Country England
Father's first name(s) William
Father's last name Stedman
Mother's first name(s) Mary
Mother's last name -
Record set England Births & Baptisms 1538-1975

Or, another credible baptism date, from Kent FHS, making her 26 at marriage:

First name(s) Elizabeth
Last name Stedman
Baptism year 1729
Baptism date 05 Mar 1729
Father's first name(s) John
Father's last name -
Mother's first name(s) Mary
Mother's last name -
Place Lenham
County Kent
Country England
Record source Lenham baptisms 1558-1911
Record set Kent Baptisms
__________________

NA

Their marriage from Family Search:

Name Jonathan Gillett
Spouse's Name Elizabeth Stedman
Event Date 07 Nov 1756
Event Place St. Mary, Chatham, Kent, England