I'd do the total surprise thing. Watch what colors they both tend to wear a lot...check out the colors of accessories, etc. and fly from there. You could also take her shopping with you for fabric, and purchase something she likes, but don't tell her it's for her...
You can pretty much tell from the things they have whether they're country, Victorian, modern, etc...
And then have fun with it knowing that since she's hinted about it that she's going to love it!