All visa and amex prepaid cards that I know of have fees but they aren't generally a whole lot. One that I like is the Visa Buxx card which is designed as a spending tool for parents to give their teens but it can be reloadable using a miles earning credit card. It costs $15 to get and then a couple of dollars per each $500 load.

Most other one time use visa/amex gift cards have similar fees (generally $8-10) and cannot be reloaded. They may or may not be able to be loaded with a miles earning credit card...it generally depends on which card you use and where you shop. There is no hard and fast rule to find out. I called my credit card company and put a block on the cash advance feature to prevent a cash advance going through on my credit card without my knowlege (I can always call to remove the block if I so desire).

Other than that you may want to consider using an airline's shopping portal to buy a giftcertificate.com supercertificate. Again you'll have a nominal fee but then your wife can redeem the super certificate for gift certificates to hundreds of different stores (both online and offline). You can double dip for miles using this technique. Right now AA's shopping portal gives you 4 miles per dollar spent on top of the miles you'd earn from your credit card.

Hope this points you in the right direction...there really isn't a whole lot to choose from. If you want to make sure your wife spends the money, I'd chose the giftcertificate.com as there is no easy way to get cash out of the cards. The Visa Buxx card can be used at an ATM.

Happy Holidays