SPOILER
though it was ballshit that she could wipe out whole cities and blow up whole fleets of bombers; if she could do that how come she couldn't win the war? =P Nothing could harm her, anything she attacked was annihilated. I'd just aim her in the direction of whoever the enemy was and destory all their major cities. They'd be happy to sign a peace treaty then.
This is exactly what she did; the reason for the massive assault towards the end, ultimately was because those forces had nowhere left to go - everything else had been annihilated.
My theory was that the enemy was actually the anti-spirals who were pretending to be an aggressive nation and kept producing limitless amounts of troops, planes, tanks (U name it) for whats her name to destory. Yes, im semi joking but you'd have to be psychotic or brainless to fight a war with a country that had her in it =P
Not brainless, desperate. Her powers kept growing, and the nature of the war meant that it eventually escalated to a point of no return; in a nutshell, as Chise's power grew stronger, attempts to incapacitate or kill her intensified as the threat she posed became ever more apparent. This lead to a growing desperation on both sides; the Japanese would use Chise indiscriminately to strike at their enemies (including vaporising their own cities) in an attempt to stall the invaders, and they in turn were forced to commit ever larger forces. By the time Chise's powers finally go out of control, well, see my first comment.
As for why they don't surrender earlier, the rest of the world is, at the time of the series, no longer hospitable; the exact reasons are never really elaborated upon, but presumably the land can no longer support mankind for a prolonged period of time. Hence, the invaders have to claim Japan if they're to have anywhere to live, and the Japanese are evidently not too keen on sharing.
