As I said earlier, the point is that it has been proven that she gave false testimony to the grand jury and, as far as I know, DSK hasn't.
That is the only relevant point to come out of all this, and that is what will bring the case down. Whatever her reasons for doing so, the jury would not be able to convict DSK 'beyond reasonable doubt' now, surely. This business about whether prosecutors do or don't want to prosecute rapists is something of a smokescreen; it's irrelevant now.