Am I Right in guessing this is an easyjet flight?
Sounds like ur friend made a miss-ID in which Mrs c was checked in as Mrs a. This happens often but is usually rectified when the actual person comes to check in. STS don't need a boarding pass to check a bag as they are issued a new one after checking a bag in. It is an easy mistake as I have saw this happen alot. I hate pooled baggage I once saw a dispatcher want to remove someone and cause there was 17 of them and it was a ULD job the dispatchers manager overruled and let it go.