She succeeded in every other world? And what did she get from it? The only thing she got was the number "34" picked for internet theories. Not even her name is of any importance after the great hinamizawa disaster. Probably she had to commit suicide after that to erase the last bits of evidence.
Defeat was the best that could happen to her.
Besides, what is so unbelievable about kids defeating soldiers? (even though they didn't defaut the Yamainu, they were about to lose if it wasn't for the Banken)