Jemma joined Arsenal in December 2014 after impressing for Bristol Academy in the Women's Super League.
The defender began her senior career at Plymouth Argyle after progressing through the club's Centre of Excellence before joining Bristol Academy and then Birmingham City.
Jemma then rejoined Bristol after a season and established herself as a first-team regular in the Vixens' back line. While at Bristol, the former England Under-17 captain was named FA Women's Young Player of the Year in 2011. She also collected the Goal of the Season award for a long-range free-kick against Doncaster Rovers Belles.
Jemma also has UEFA Women's Champions League experience, playing for Bristol in the qualifying round of the 2011/12 competition.
The defender is a regular for England Under-23s and was named in Mark Sampson's first senior squad, although she did not make an appearance.