Ly'lac being a Doom player is definitely a major possibility, though I'm not particularly sure yet. The ~Ath book, "black thumb," visions of certain failure, themes of destruction, and general "doomer" mentality definitely raises a bunch of flags for her being Doom. But, there are other possibilities. Most of the tells implying that they could be a sign of being a Time player, as they have the same relation to death and fate as Doom does. Also, the idea of a "ticking time bomb" does relate more to time than doom on paper. However, this is less likely considering that they would break the 'time players are red' tradition if true.

There's also the possibility that they're a destructive space player; as you may have noticed, they are LITTERED with Jade parallels. But it's less likely they are jade and more like their struggling to be Jade. Jade could make extremely advanced tech, and they can only make primitive tech. Jade grew all the plants one could ever desire, Ly'lac tries and fails. Jade actually listened to the 'shit on your desk' command, Ly'lac did but couldn't show it on-screen. And she's known about her destiny since childhood, but has seen it as something weighing her down instead of something which could pan out for her. A lot of these are traits which can be vaguely tied to space as well as Jade. So, I think it's plausible that Ly'lac is a space player who's gonna struggle with her aspect in the same way Jade does.

(And of course, just to make my bias clear: my doubt of DoomLac stems from me strongly believing in the theory that the omega kids will use the humans' unused classpects. If any of them get a classpect that shows this being not the case, or repeat classpects are confirmed, then I'll be on-board with Doom Ly'lac.)