What you could do is, is introduce her to the horse that you are thinking of buying, and telling her how great the horse is (when you do this, you should have had the vet check, test rode, talked to other sources that know the horse). Tell her you are thinking about getting this horse. if she loves the horse and everything, you could probably get it. This is what my dad did when he suprised my mother with a horse. However, my parents have been married for over 20 years so it's a little different. I don't know if I would go and get her a horse she doesn't know about.
About the other things, a horse that is already registered in the AQHA is desirable, if you want to use the horse for showing in AQHA shows. People who want to compete in the AQHA shows and are horse shopping find this desirable because then they don't have to register the horse themselves. I believe it is just changing the ownership on the papers (there may be more to it.)
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