I don't care if she was driving a Smart of a Beemer, it is still rude. With that said, I wouldn't get bent out of shape about it. Nor would I finding shocking that another Smart owner would act this way. People are people.
Just because we share the same type of cars doesn't mean we have the same happy-go lucky attitude.
Personally, I don't smoke, but there are some

Smart owners on this forum that I'd like nothing more then to send a cigarette butt their way if I saw them on the streets (no I'm not naming names).
That lady was rude and she had a Smart. I'm sure she's not the only one but she's definitely in the very small minority so don't let that affect your friendly gesture towards others this week.