Oh this is going to be one of those things where a character blames themselves without good reason, right?
Oh. Oh no. It's so fucking rare for the self-loathing to be justified.
Self loathing can't really be judged on whether it's justified or not in this manner. It's perfectly understandable that the act of drinking might make it more her fault or push the situation into the grey area or even over to it being absolutely her fault, depending on how the rest of it went.
It might be that she collided with another driver that was also under the influence or driving recklessly, she might've really not had very much alcohol and been under the legal limit, she might've been distracted like another commenter pointed out. Before we judge whether it was her fault or not it's good to have all the facts.
People will find any reason to blame themselves in situations where they believe they should've been in control, but that isn't always the case even if you're doing everything right. If a person as young as her was actually completely at fault we still can't say that she should loathe herself so much or that it's a good thing.
What I'm trying to say is that as far as we know she is the only person to live with the consequences of this incident and saying it's her fault or that her self loathing is a good or appropriate thing isn't really the case with situations where the person wasn't acting with malice.
This situation is more of the 'wrong place wrong time' with some negligence sprinkled in, which isn't really surprising since she was young and her risk managing isn't fully developed, not excusing it but saying that with the remorse she feels being far beyond what she deserves it's not fair to blame her as an observer.
To add to this if her self loathing motivated her to do something good like advocating for safe driving, organising an AA group to help prevent incidents like this happening again or studying to be a doctor so she might be able to save someone. In that case it would be a good thing since it brought more good. However her role in the accident is so far unconfirmed and she didn't have any malice in mind as well as her age means it isn't fair to say it's justified.
To be clear you might also hold this position and just didn't want to type it all out, or you might mean that it would be hard to argue for her not being at fault to her specifically, as she is most definitively biased and her blame won't be entirely logical. I just felt I needed to write my thoughts out on this since it's a complex subject and I felt your wording wasn't sufficient. No hate just wanted to write it down somewhere.