Elena was going to argue, but Deucalion made it pretty clear he wasn't going to heed any of her arguments. In the end she let him pay for everything, but felt awfully guilty about it all. She'd have to insist that the books were his, and then she could simply borrow them from him to read them.
"I can drive for that trip, too. If--If you want me to," she added, almost shyly.