My daughter flew AMS-LGW on Friday night on a rammed A321. She was in group 9 and ten or so minutes before boarding the gate staff announced, "we have a completely full flight, therefore all baggage that will not fit under the seat in front of you will need to be checked-in here for all passengers in group 9. However, you will then be able to board at the start of the boarding process".
Quite a few of group 9 eagerly came forward and surrendered their bags and everyone waited for boarding to start. A more senior person then arrived at the gate and overruled this and started with the usual people with special assistance, families with young children, then groups 1 etc etc. Group 9 were the last to board, even though they had surrendered their bags and had been told they would be the first to board. My daughter said they were some pretty angry pax at the gate.
This isn't a grump at your or your daughter but I think making them wait is the best thing. I have been on busy flights where group 1 is held back for ages as loads of people pre board due to handing bags in.