Knemo, in situations like this, I always find it easier (and considerably less stressful) to just write down their number and call the cops. Even if you don't get to lay charges (I don't often get to out here because I tend to avoid "accidents"), you might get them to give her a lecture about her driving, which is probably more likely to make her change her behaviour than shouting obscenities.
As far as laughing at her goes, that really is a good response. To once again quote the greatest song lyrics of 2003:
"If I was tough enough, I'd knock your arse to the floor, but I'm not, so I'll just laugh and make a run for the door".
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I am clinically insane. I am proud of it.
That is all.