MAN, I am so there right with ya! Ditto.
That being said, just try to remind yourself she is the one weight a challenge she needs to get through and the best you probably can do is gentle reminders on what she does that's good, like when she is patient driving and elsewhere, not pointing out when she does something wrong. Having been one, I can say first hand that loving someone with anger issues and patiently working through the lengthy process of (hopefully) helping them work through to the other side of it will make you believe there is a His, lol. It's one of the hardest possible relationship challenges because even when it is obvious to all around, it doesn't have quite the same stigma as like a drug or gambling addiction or infidelity - where a certain amount of peer pressure encourages them to get past it. It is one of those things where the person with the issue always has someone else they can point at as the real problem. I wouldn't recommend pointing out that the other person isn't it, maybe more of an ,"Yeah, I know they are wrong...but who you are in response to it is a choice you can make, and do you really like the person you are being *right now*?"
Just my 2 cents, from someone whose spouse got them to the other side...