Holy evolution, Batman. In Pure, Lyda is mainly just a pretty girl who takes Partridge to the dance… although she starts getting fierce towards the end. But right from the inception of Fuse, Lyda is a warrior. We first meet her when she's under the protection of the mothers:
Lyda wants to see Partridge, desperately, but she likes it here. They've started her on combat training and hunting. Her muscles have grown strong. Her aim is good. She's learned to lie in wait silently. It's dangerous, but strangely peaceful. (5.12)
We'll admit it: even though there's really no character in Baggott's trilogy we'd like to face in combat, we're maybe the most fearful of Lyda. She's silent but deadly; she's basically a ninja assassin that's perpetually in stealth mode. And not only is she strong physically, but she's become hardened mentally:
She isn't like the bird she once made of wire, locked in a wire cage. Her bones are not that frail and malleable. She's a hardened knot all her own. (24.2)
But let's not forget about Lyda's burning desire for Partridge. Despite her faithfulness to the mothers and her yearning to live outside the Dome, she can't help but feel weakened without Partridge. Even her strongest moments are followed by feelings like:
And as good as this feels—an incredible freedom, like nothing she's ever felt in her life—it's met by the sharp ache of Partridge's absence. And for a second, she also misses the person she was before she told Partridge that she couldn't go with him. (24.2)
Lyda defies the subjugation brought upon her by the Dome, but she's still human. And because of that, she's not exactly the warrior she so desperately wants to be.
But that's probably a good thing. Lyda is a better human—and a better character—because of her juxtaposition between being sweetly romantic and being a human lethal weapon. Throughout Fuse this juxtaposition is further underlines by the fact that she becomes preggo… with Partridge's baby.