Help a guy out!

I am looking to buy a really nice dress as a gift for my GF but I have no idea about women's fashion and which brands to go for. My GF is a 30 yr old girl who wears XS or S size clothes generally and I am based out of the US.

Which brands would you recommend I look into to get her something nice in the $100-$200 budget range?

Extra brownie points if the packaging is really fancy or else I can gift wrap it up myself.

TIA!