It is her home. That's where she's from. Why should she leave?
What do you think the chances are that she, and other people in her situation can solicit help from the armies of the world to take back that country? You can be certain that the European nations don't want to, and I strongly doubt that the US would get involved. We'd have race war overtones here, and besides, we've got our hands full with the Muslimes.
That pretty much leaves Canada and Australia to do the fighting, and I doubt that's going to happen. The biggest difference between what happened in South Africa and the United States is that over here, our European ancestors killed off most of the original inhabitants.
We face the same problem with those who would re-conquer from the Southern flank.
For the same reason German Jews left Nazi Germany.