It happened sometime in between researching lore and falling asleep together in that cave and watching everyone else in their lives triad-up. Stiles didn't think of Lydia the way he used to. Instead of the perfect goddess that he would kill to be with, he saw mussed hair and secret tells like the way she held her pen or sometimes couldn't step on cracks. Derek saw a lot of Laura’s strength in Lydia, in the way she never quite said what she was thinking, and it made him sad, but it also made him want to bare his throat to her, so he did. Lydia saw two boys as lost and lonely as she felt, both so loyal to her and to each other that she felt like a fraud seeped in gratitude. She saw a boy who needed a mother and a boy who needed an alpha, and she wasn't those things, she didn't want to be those things, but when she reminded Stiles to eat and when she pushed Derek’s head down into the mattress, she felt good.
Lydia bought the strap-on after Jackson left and she felt the need to go looking for a distraction. Her name was Penny and her lips were sweet and her skin tasted like salted caramel, but the next time Lydia found a distraction, his name was Ben. And then Will, and then Aiden. After Aiden, Lydia didn’t feel the need for more distractions.
The first time Lydia watched Stiles fuck Derek, she couldn’t help but stare at Derek’s face. Even though Stiles was rough, for the first time, Derek didn’t look like he was in any pain. Lydia wanted that power, too. She dug her strap-on out from her closet, cleaned it up, and told her boys, “I want to try something.”
Stiles smirked, but Derek trembled and murmured, “Fuck,” with this reverence that Lydia would remember when she was thrusting her way through her second orgasm and out the other side, keeping up the rhythm for Derek’s sake. When Stiles finally shoved his hand between the mattress and Derek’s cock, Derek came, shaking and crying. He slowly relaxed under Lydia’s hold on the back of his neck and when Lydia pulled out and let him up, he looked almost drugged.
"Baby, are you alright?" Lydia asked, unstrapping herself and then sitting on Derek’s right as Stiles sat on his left.
Derek nodded and leaned his head against Lydia’s chest. “Good,” he said. “I-yeah. Good. Thank you.”
Lydia rolled her eyes, but she held Derek close and ran her fingers though his hair until he sagged against her, asleep. Stiles helped Lydia set Derek down against the pillows and then curled up behind her.
"So when do I get a turn?"