Luckily the fashion for "girly bikes" has meant a rise in wicker baskets.
What you will need to do first is to decide how to fit it, will it be removed for shopping or when parked, or permanett.
One that fits by straps will be slow to remove, one that fits with hooks or a "Klick-fix" will remove quickly.
Then of course there is size....
Your best bet is to take wife and bike to the local bike shop(s) and see what she likes
