Sure it sounds like her waters broke, she was in labour and delivered 2 days later. By which time the baby was infected and sadly had died. She had no symptoms. So she had no treatment. If her baby had not died then at birth it would have been observed/swabed etc etc, and had antibiotics if needed because of the prolonged rupture of membranes.
It is horrible. She may very have had a swab in labour, but they take 48 hrs to come back and by then the damage was done. Most babies are born alive in that situation.
Like I said I am not saying it is right but there is nothing to say that testing her at 36 wks would have picked it up. If she had tested neg at 36 wks they would have given her the exact same treatment she received in labour. If she was lucky enough to be picked up then things may have been different, and I am sure she would have received treatment in labour.
There in lies the argument. To test and maybe pick it up, or not to test. That is why home self GBS test kits do so well.