The 23-year-old was previously at Lincoln Ladies having started her career at Leicester City before a spell with Leeds United in between.
Allen has represented England from U15 level through to U23s with the highlight of that international experience being the Three Lions' lifting the 2009 UEFA U19 Championship; a team that also included new Blues teammates Rebecca Spencer, Jade Moore, Izzy Christiansen, Chelsea Weston and Kerys Harrop.
Commenting on Allen's arrival, Blues Ladies boss David Parker said: "I'm delighted we have been able to secure a deal for Remi in what is a great coup for the club.
"Remi is a combative central midfielder who has been a shining light in Lincoln's side for the past three seasons and will add another dimension to the side next season.
"Often overlooked is her technical and goal-scoring ability which gets less plaudits because of her aggressive style of play. What is also key when recruiting any player is their character and how they will fit into the group and with Remi its a perfect fit for this football club both on and off the pitch." To find out more about Blues Ladies, visit: www.birminghamcityladiesfc.co.uk.