Is this a Good Idea for a Story?

I like this idea. it is very interesting. You should also expand on the part about her love and childhood friend. Those could also have their own hard pasts. I would read this. This sounds like the begining of a series. For excample, This could focus on C (nice spy name), another on B, another on A, Slowly bring them together reforming the world. Reformig the world is a typical part of a post appalyptic world book.