Amex has some of the best lost and fraud protections... Maybe you can get her a downgraded Green and still keep the Platinum.
Green doesn't do much other than no preset spending limit.
Gold has free travel upgrades.
Platinum has travel + "concierge" service.
I think that's pretty much the differences between the 3 cards besides the annual fees.
Wow, concorduser, I wish you'd been my daddy back in, let's see, 1970! I wound up with a 1963 Plymouth Belvedere.
I agree with the others, you're covered with either card in case of fraud.
I suppose the things to consider:
--could your access to your Plat be temporarily limited if she lost hers?
--would she have any need for the plat features? (for instance, she is in a school choir or art class that might travel around the US or abroad)
One thing that I like about my Gold Rewards Plus is that up to 4 AU's are free, and that was handy when I put my youngest on it when she went to Ireland. My card went to Ireland, Wales, and Paris, but I didn't. Something wrong there.
Why not go for the Gold AU?