I'm intrigued as to who was being unreasonable (if anyone) here.
There is a queue of about 7 people waiting to pay at a small supermarket attached to a petrol station. Three tills are open.
Woman A is number 6 in the queue and realises that she has forgotten something so leaves her basket at the side of the aisle and nips off to get forgotten items.
Woman B is number 7 in the queue and moves up to take her place.
When woman A gets back to the queue, it has reduced to 2 people. Woman B is now number 2. She doesn't offer to give her place up to woman B.
There is a bit of follow-on too, but interested to see whether MN thinks there is anything unreasonable in this scenario so far.