This 檳榔西施 is very cooperative, and seemed happy to have pictures taken. A few of us took pictures with the girl. I asked if she would pose for me in front of her store sign, and she gladly posed.
At the end, I gave her a little tip of NT$200. I later asked the driver if it's common to tip. He told me it's OK to tip, but did not say if it was common.
My friend explained that these girls do not have much schooling, and by dressing sexily selling betel nuts and drinks to drivers, they can make maybe NT$10,000 per month. This is considered a very decent sum for what they can or willing to do.