The wreath style piece looks lovely; I would assume the necklace is threaded with Sterling wire... Since the pearls range from 4.0-6.0mm, and there is two or three pearls per row, I would estimate that the total width of the piece would be 1/2" or so in the front- which should be just fine for your girlfriend. :
I like the 'platinumized' term- that made me giggle a little, but it's a great idea! That the platinum plating will prevent the sterling from oxidizing and tarnishing is the best part about it barring the design!
Q: How are the pearls 'held' into place? I don't see any crimps or wirewrapping keeping the pearls stationary on the wire. If they are allowed to slide back and forth, then wear and tear around the drill shaft should be taken into consideration.