My initial theory was that she is saved from the Daleks in a not too dissimilar way to how he saved himself at Lake Silencia where he saves her before she joins the Alaska and replaces her with a ganger duplicate. But reading an interview yesterday Moffat said that they are going to do the "losing a friend and making a new one" story properly - maybe he means that literally and Oswin isnt actually human at all and she is in fact a ganger duplicate that he scans.

I definately think there is a part where she is selected because of the hopelessness of her situation. The one constant of the Doctor is his companions always end up worse off in some way, though a few have a fairly good ending, and Oswin having no future at all let alone a positive one is the perfect companion because she cant "lose". She might not even know she was Oswin or what happened to her original personality.

The simplest theory of course is like Gwen Cooper from Torchwood they will have the actress play two characters and just give a throwaway line about them being related seperated by a few generations, but it just makes no sense to me what that adds to the story to make them cast her as a short cameo to then die sacrificing herself only to be effectively "reborn" as a new character entirely.

In Asylum of the Daleks her character is Oswin Oswald. However as the companion it is revealed by producers and the BBC she is called Clara Oswin. I just refuse to believe given the hints of how "this isnt your normal boy meets girl" from Moffat and how its one of the bigger mysteries of the show it is as simple as she is related to the Oswin who got converted by the Daleks.