Do you have The Dress at DAZ? It comes with a cowl, and one of the headpieces (sold separately) is a veil. They're PC items.

The Dress itself is rather too form-fitting for a nun, but perhaps you could find a different dress to use with the cowl and veil.

Also check out the swordbearer monk's costume for M3 at PoserFashion.net. It's dynamic clothing, and so could probably be adapted to Vicky pretty easily, if you have P5 or P6.