Queuing Etiquette Gone Awry

I walked into a Ross store to return some items and found several lines to choose from. The one I went to had a young woman waiting for two different lines. As I had just been in the store a couple days prior I knew that they wanted customers to pick a line to stand in. So, feeling bold, I asked the woman waiting which register she was waiting for. She replied whichever one was fastest. Then I said something to the point that there were two lines and she needed to make a choice for one register or the other. When she just stood there I went ahead and went to the left since that was also the one at the customer service counter. I don’t think she really liked that because her line went faster and as soon as she was finished she turned to me with a look like, “You’re such a bitch.” I simply smiled and she continued walking out.

Is it inappropriate to ask someone to choose a line? That’s like driving down the middle of the highway to make sure one lane was faster.