Nothing was common about Lydia's feelings about Scott and Allison. It was like a million tiny things under her skin; they wouldn't let her go unless she spent time with the people she loved. She loved the chaos of being in love.
Headcanons under the cut.
Allison teaches Lydia how to fight with simple hand-to-hand combat. Lydia loves it and Scott likes to watch as Allison and Lydia kick the shit out of each other. Lydia loves to kneecap Scott in a joking way
Lydia and Allison share clothes and jewellery. Every so often, they will give one of their necklaces or bracelets to Scott to wear for the day. He thinks it's fun to wear their things, almost like a possessive thing that goes both ways
Lydia refuses to go on Scott's motorcycle, but Allison loves it; she's kind of a speed demon. Scott tried to teach her how to drive it, but Allison prefers sitting behind him and feeling the wind in her hair
Scott can cook pretty well, Allison is more of a baker, and Lydia could burn water.
Nightmares are common in their house. Allison prefers to be held and connected with post-nightmare, while Scott doesn't like to talk after a nightmare. Lydia is pretty quiet after a nightmare, but likes to be held and grounded
At any party that the three of them go to, even if it's just the pack, they always arrive together and leave together. Scott likes to know exactly where they are and loves to dance with his partners. Allison is more of a free spirit but adores dancing with her loves, and Lydia is flitting all over the party and every so often will pause to press kisses to her partner's lips
Every glance that the three of them share is like a full conversation