I don't think the Snapscore modifies after she logs out of the application. The Snapscore is influenced by how much you communicate one with each other. If the score doesn't modify, then you're doing something wrong. Try using the tools available within Snapchat to increase the score. However, if you don't talk for a period of time, then the score will disappear or modify itself.
Snapchat developers provide a page related to My Score/Snapscore as well.