North dealer. I don't know the auction, other than North played in 3NT which made for a near bottom EW, because only one other NS pair bid it. Deep Finesse says it should be held to eight tricks, but I am looking at this trying to see where my friend and her partner could have done better, and it does not look easy at all to get 3NT down.
As a wild guess, NS were playing Acol, weak NT:
This is the only way I can think how they got there.
East leads the spade six, which gives declarer a tempo to set up a second spade winner. Declarer can also lead toward the club king for another trick. Added to the five diamond tricks and two major aces brings the total to nine tricks, so EW have to move quick and be very precise how they establish their five tricks. It looks like the spade lead was fatal, but who wouldn't lead a spade if this was the auction? Anyway, looking at all four hands and rewinding back to before the opening lead, I can't see an obvious way to stop 3NT, the defence can establish a couple of heart tricks with the club ace, but beyond that it looks as though whatever black suit they try to attack helps declarer as much as them. What am I missing here? What I am trying to do is go through my friend's bad scores and advise where she could have done better, and there is theoretically a way to do better here, but how, and how would even a decent intermediate find it at the table? If the killing defence at the table could only be found by a pair of internationals then fair enough, I'll put it down to random crappy nonsense.