They have a map of California spread out on the dashboard, a playlist of all their favourite songs on shuffle, and an open box of chocolates that Lydia knows she will regret later.
Allison's window is rolled down in this heat and her arm is hanging out, relishing in the cool breeze. She's looking at Lydia with a stubborn look in her eyes, and she opens her mouth to try and convince Lydia, but-
"No. I will not, I repeat, will not wear a pair of trainers. I do not care if you think I'm being ridiculous, I will not sacrifice my shoes for one road trip."
Allison sighs, because she's been fighting this argument with Lydia for over twenty minutes and is just going round in circles. She thinks she's done well to convince her friend not to bring her four pairs of nude designer six inch heels.
They compromised on four inches.
Lydia sighs impatiently to recapture Allison's attention, already missing the spotlight.
"Chocolate?"
They're a luxury box that cost Lydia 22 dollars, and there are three more in the back.
Allison nods, and accepts the sweet Lydia offers her.
She bites into it, and is hit by sharp cherry syrup, which slowly morphs into sweetness on her tongue.
Lydia grins at Allison's satisfied expression and takes a dainty bite out of her own chocolate, the caramel sticking to her teeth and tongue.
This time it's Lydia's turn to pick the music, and when she turns it to Elvis Costello's Alison, her best friend gives an exaggerated huff and rolls her eyes. But by the time Costello's voice is rolling over the line 'I'm not gonna get too sentimental,' Allison gives in to Lydia smirk and starts singing along with the strawberry blonde.
And though Lydia is one of the most beautiful people Allison has ever met, and she can solve a quadratic equation in under four seconds, she cannot carry a tune to save her life.
But they both sing along, one of Lydia's hands on the steering wheel, the other shaping into a microphone, Allison marvels that she's never seen her friend so carefree, without the constant stress of night wanderings, ex boyfriends and resurrected nightmares.
And Allison likes it, because Lydia's smile, so genuine, could make her forget about her troubles as well, and she let herself go, imagining it was just her and Lydia, on this long road, with nothing waiting for them when they got back.
They're two and a half weeks into their road trip when Lydia notices something. She notices that Allison twitches her right hand when she's impatient, that she has two small moles on her left shoulder, and that she will always ignore the coconut chocolates in favour of the cherry.
Lydia doesn't know if you should notice that much about your best friend, because Allison's the only girl who she's ever genuinely liked, so she doesn't have much to go on.
But Lydia is a certified genius and she knows that the tightness she feels in her chest whenever Allison cuddles up to her in one of their sleepovers is different, or that the sick feeling in her stomach she got whenever Jackson flirted with her best friend was not just jealousy over her ex boyfriend.
Lydia knows she feels more than she should, but she takes it in her stride, as she has with everything else, and tries to hide her reaction when Allison flashes one of her perfect smiles.
Allison makes up her mind the day before they start to head back. Lydia is stretched out on the hood of the car, white dress glowing in the heat, looking oh so relaxed and oh so perfect, that Allison decides.
She has to do it. So moves closer to Lydia, putting down her book, and drawing the attention of her friend. Lydia sits up, and Allison does it.
She leans forward, determined, and presses her lips to Lydia's. They are soft and warm but Allison starts to pull back because Lydia hasn't done anything but then Lydia's mouth is on hers, and her hand around her waist, and somehow Allison's hand has found its way Lydia's back, and oh damn, her white dress is backless.
Lydia leans even closer to Allison and lets the warmth overtake her. She presses up against her and when Allison feels Lydia's hand starts to wander upwards, she gasps, and Lydia takes full advantage.
And all Lydia can taste is cherry syrup, and they both can think about is how good it feels to finally have each other, finally, together.