Woman at the supermarket

At the supermarket last night, we were going through the express check out along with quite a few other people. In front of my husband and myself were 2 ladies.
There were 2 check outs open, so there should have been 2 separate lines, like there has been for over the 6 years I have been going there. The woman with the trolley filled with about 6 bottles of wine and nothing else, although well presented at the front of this strange line, and another young lady just behind her. The young lady noticed the next person was nearly finished and since the woman with the trolley was not moving up decided to move forward.
The woman with the trolley grabbed her arm and basically told her that she was not allowed to jump the queue. I heard this and said "there should be 2 queues here", she turned around and said it was supposed to be merging like a zip, and then added as an after thought, "well it should". I said "since when?" and the young lady who she would have embarressed also agreed with me.
But we left left it there, while this woman was emptying her trolley she looked around at the other isles to try to back her claim, to no avail.

I was soooo cross, she has embarressed a young lady in front of a large queue, she had actually broken the law by grabbing the young ladies arm, and who was she to impose her sanctions on others? Well I have now vented and I am sure Karma will bite this woman (who goes shopping only for wine and to assalt people and insult people) in the butt.