The fourth flag, all the way on the left, which you don't mention, may be the Lion of Flanders.

If you look at the coat of arms, for some reason (as this is South Holland, just near the border with Flanders/Antwerp, and not actually Flanders - perhaps the saint or the church has some connection?) the bottom right quarter is a Flemish Lion with a red diagonal. Perhaps that's what the leftmost flag is, considering the third flag (the one here asked about) shows the emblem of the bottom left quarter of the coat of arms.

If you go to the church's website, the saint's statue also has a Lion of Flanders on her breastplate: https://www.liduinabasiliek.nl/pics/liduina-135x190-pkmt.gif