Her batting average wasn't too bad there either--it's just the most notable disaster was a huge one and involved 2 grandchildren. :-/
She did well with:
GV&QM (and before that Eddy & QM)
Louise & Fife (in allowing the marriage even though he was 'just' an Earl at the time; she raised him in rank)
The other grandchildren she didn't have much imput with except to give her approval (which, granted, carried some weight) as with VMH & Louis Battenberg which she championed in the face of anti-Battenberg prejudice.
Plus, she had strong reservations regarding the marriages of Ella/Serge and Alix/Nicholas, which, sadly, turned out to be very prophetic.