My wife, who has a narrow foot loves and will not ever change to another brand, her Chota wading boots. I also have a pair and they are great boots. Excellent fit, light as a feather, great ankle supprt and good ankle cushioning to help keep gravel and sand out.
My daughter loves her Korkers that I bought her last fall. She has very tiny feet and the Korkers fit to a tee.
Best bet, take your wife shoe shopping, if possible. Take neoprene socks or her waders and have her try on the boots and walk a bit in them. Nothing ruins a fine day of fishing like boots that hurt your feet or don't give proper support.
If that's not possible, have her foot measured at a shoe store wearing her neo socks or waders. Most shoe stores will be helpful, especially if she's a return customer. Then order the appropriate size.
If your stuck with mail order, pick a dealer with a liberal return policy so you can experiment until you find a pair that fits and supports her foot well.
REE
Happiness is wading boots that never have a chance to dry out.