Sophia Burnes, or is she? Wait who is she?

When the team go on a mission to take down a remaining Red Room facility, they bring someone interesting back. Who is she? and why did the Red Room want her? Are all questions S.H.I.E.L.D wants to know, but first lets just start with her name... This story is set after Avenger but before CAWS, the Agents of S.H.I.E.L.D 'bus' team may make an appearance. Contains all Avengers&more.