Highly-rated England international Christiansen rejoined Everton in January 2020 having started her senior career with the Toffees 11 years earlier.
She was unable to make an Everton appearance during the 2019/20 season, however, owing to injury and the WSL being ended early due to the coronavirus pandemic.
A product of the Manchester United academy, she initially signed with the Blues in 2008 before moving on to Birmingham City the following year.
Christiansen spent five seasons in the Midlands before completing a move to Manchester City, where she won the FA WSL Continental Cup in 2014.
In 2015/16, the Macclesfield-born midfielder's form led to her being recognised by her peers as she was named PFA Women's Players' Player of the Year.
Christiansen's form over four campaigns with City drew the attention of French giants Lyon and a switch to the then European champions was sealed in July 2018.
In her first campaign with Les Lyonnaises, Christiansen helped the team to achieve a league, cup and Champions League treble.
Contracted until: June 2021