Thats just horrible and petty minded of her. I wouldnt lower yourself by resorting to the petty mean come backs that have been suggested. Life is not one long game of 'who can come up with the cleverest meanest comeback'. Thats just for TV programmes.
I feel the same Ballistic. I dont know why people think its clever to be rude - because they have very low self esteem I guess, and have watched too many TV shows where its funny to make a nasty comeback to someone.
I was once sat at a roundabout and was waiting to take a right. I nearly pulled out when a car came very fast from my right, and I stopped to let him pass (his right of way). It was clear I was going to pull out, but had stopped in time, but as he went past he made the most violent face and hand gesture to me. Well I thought it was way out of proportion to my 'crime' of nearly pulling out on him ( I was well clear and didnt cause him to slow down or move his position on the road in any way).
So I followed him home. I pulled up behind him ands as he got out of the car I said 'I am SO sorry I nearly pulled out on you, but I misjudged your speed'. Well he was falling over himself to apologise to me, he had a million excuses for why he had been so rude, and begged that we were now 'friends'.
I knew If I had shouted at him 'what the hell do you think you are doing making that hand signal to me blah blah blah' it would have been an all out war of words with him.
I suggest next time you are in the situation where someone has been obviously rude, be genuinely apologetic in a way that makes them reflect on their own petty small minded behaviour. (course it might not always work!)