Since this is a huge purchase, with so many options for size, style, tone quality, etc., I am not sure it's something one person can choose for someone else.
But since people who want to buy harps for other people should never be discouraged (LOL), here are some suggestions:
1. Rental?: A six month rental would be a fabulous gift. Contact your local chapter of American Harp Society (if you are in the USA), or other harp institutions or harp university programs to find out who rents in your area.
2. Harp Column magazine (online or print) has harp ads, occasional articles about harp purchase. Makes a great gift too.
3. www.harpspectrum.org Has articles about harps.
While used harps are often a great option, you need to have an experienced harpist look at it. I and many harp teachers I know will evaluate a used harp with you to look for structural flaws, string condition, and other possible conditions affecting its value. Unlike most other instruments, harps sound better and better for about 70-100 years, then they explode or need costly "rebuild" services.
Don't buy the cheap "Pakistani" harps you see online; they are garbage.
Choose between lever and pedal depending on the preferred genre of music that will mostly be played.
With lever harps, get full levers and make sure you get one that takes the kind of strings you like (nylon vs. gut vs. synthetic). I know, this is one of those "how can you pick for someone else?" situations, but at least know that there are vastly different kinds of strings.
You are a very nice person! Good luck!