Before you continue, I am going to drop a SPOILER ALERT for Rick Riordan's The Son of Neptune, though if you read The Lost Hero, I don't think I've revealed anything you didn't get from that book.
As I was reading The Son of Neptune to my infant son (he's not into pictures yet, so he's just as happy to hear my voice go on about Percy Jackson as the Runaway Bunny) my husband asked me "Wow, is Gaia really that mean?" and it got me thinking about the nature of Gaia.
First let me say that I've never been 100% happy with the way Rick Riordan portrays the Gods in his books, but hey, it's fiction and I'm not going to gripe. But back to Gaia.
Mr. Riordan has a few things right, or at least we agree on a few things. Gaia is a sleeping Goddess. She is not a Goddess who spends time worrying about what mortals are doing. Gaia is a primordial Goddess, born of Chaos. The children she created are forces of Nature. She had her husband castrated in order to release them. Then the second generation, the Gods of Civilization, rose up and subjugated them and She created more children to defeat them, and they failed. Then Gaia slept. Meanwhile, civilization grew under the Gods of Olympus.
So, if Mr. Riordan wants to portray her as vengeful, releasing primordial forces in an effort to destroy Civilization and the Olympians, well, I don't see that as so far fetched. Is She evil? No, of course not. She's just Nature and, frankly, Nature would be a lot better off without humans and civilization.
I do, however, think it's kind of far fetched that Gaia would open the gates of Death. (Although I realize it was necessary to release Her children trapped in Tartarus.) Death is necessary to maintain the balance of Nature and I would think that bringing and end to Death would only make matters worse.
So... the answer to my husband's question (from my point of view) is Yes and No. If Gaia awoke, people would die, hell yea. But I don't think Gaia would take a personal interest in who was dying and she likely wouldn't try to use any individuals to accomplish her goals. No, I think she'd simply shake us off like so many fleas and whoever managed to hold on would hold on and whoever didn't, well, that would be it.