Finnigan, 19, joined the Toffees at the age of nine and has since progressed to become a regular first-team player.
She helped Everton win the Women's Super League 2 Spring Series, with the club since selected to join the top flight for 2017-18.
"I can't think of a better way to mark that anniversary." Finnigan said.
"I played a lot during the Spring Series, which was great for me, but I do believe making the step up to WSL 1 will boost my performances. It will help make me the player I want to be."
Defender Megan Finnigan has signed her first full-time professional deal with Everton Ladies, a decade after first playing for the club.