If your wife does not have any experience with horses, buy her riding lessons first. After 6 months to a year, then start looking for a horse for her.
I have had many parents join our 4-H club who want to buy a horse for their child. They don't know anything about horses and the kid doesn't either. I give them the same advice as you.
Do not get a rescue horse. Very often those have huge holes in their training and are a disaster for an inexperienced person.
What is your price range? For a well trained horse that knows it's job and won't get upset if the rider makes mistakes, expect to pay $2500 or more.
Honestly, buying the horse usually the cheapest part of the equation. They require hoof care every 6 weeks and vet care (vaccinations, deworming) is more expensive than cattle. When you buy a saddle, don't buy a cheap foreign made one. A good used well made western saddle will cost $500 or more. The good new ones are over $1000. And I am not talking about a show saddle.
I really understand about your wife wanting a horse. We have 6 and I've loved horses as long as I can remember.
ETA: Even since your wife had a horse when she was younger, still offer to get her riding lessons so that she will be in shape when it does come time to shop for a horse.
I don't know your wife and I don't mean to sound cold, but just because a person had a horse in the past does not mean that the person was a good rider. Safety first