She went poking around in spooky ruins that had sealed themselves off again, then went poking around on the columns even more in the spooky ruins, all on her own and without waiting to see if Pioneer II would try and find out what was going on. She didn't exactly make the smartest move there, even if the army woke up the world's most mistranslated enemy.
Though the stuff the army was fighting in the ruins might not have been (directly) because of it. Might have been the defences, which would explain why the hell something came all the way out and started killing the Forest wildlife, and then the Ruins sealed again. So the place got wiped out as a defence, Rico opens it up again and gets possessed. As her ruins info says, the place is still operational and it is meant to be a sealed casket.
Though it's been a while since I played in detail, the other implication is that you're only a few hours behind her at most by the time you get to the end.