That if was only when she saw Mat, Perrin, Rand, Egwene together, was it an if. Which is clearly the Last Battle, before Rand entered the Pit Of Doom, which easily could have gone either way.
Rand, Nyneave and Moiraine alone showed certainty, enough to know that what those three were going to do was important. She just had no idea that sealing the Bore was that important a thing to do.
All the spark viewings fighting the darkness were their actions from the Merrilor meeting, to the Last Battle, to the sealing of the Bore, and only when Moiraine, Nyneave and Rand were together did the viewing show the sparks winning.