Rachel was driving the car, and she'd had a beer or two, nothing much. She wasn't even over the legal limit. She's driving because Keith doesn't drive, and besides he's had more than she has.
She'll always wonder if he'd still be alive if she was completely sober. If she'd been a fraction of a second faster, if maybe she would have seen the driver swerve.
The guy who hit them was three times over the limit. It was his twenty-first birthday and at his trial Rachel can't even meet his mother's eyes.
She doesn't actually give up alcohol until Ana offers her a drink even though she's still on painkillers a week after. It just happens to be what Keith was drinking that night (she knows because she was stealing sips) and she has to spit it out right there.
After that, she can't stand the smell of alcohol. It's like a hangover and a panic attack and the taste of grave dirt all rolled into one. She pours all her bottles down the drain, and refuses to even get a coke in a bar. No one comments.