I can see cur mix with the pictures TruckersMom posted. Do you know where she came from? I don't really see boxer, I'm guessing they said that based on color. She looks like she has something a bit more fine boned. But it's hard to say without a pic of her standing. Does she have a trim build? Or is she more stocky? Maybe a lurcher mix.
I know a cur is a 'purebred' hunting dog. I don't know how strict people are with their breeding. I've never seen them in person and while I can kinda see that look in this dog I think it is more of a Heinz 57 mix. Maybe I just suck at trying to get my thoughts across in text.