Using Mac based iTuners account to buy for someone else's iPad

While you can do what you indicate it may make sense for her to simply set up her own AppleID and account rather than have to go through the complexities of you doing it, particularly since you do not indicate you have any kind of mobile device yourself. You run into layers of having to associate devices to your computer and set up family sharing etc. People do it all the time but usually where multiple people in a family unit want use of a purchase.

I can relate to the card concern. I don't have an iTunes account but with other accounts I make the purchase then delete the card information. It is a bit of a nuisance (and I am sure the companies are very disappointed I don't have "one click" purchasing set up!) but for the two or 3 purchases I make a year online it is worth it for peace of mind (if you trust them to really delete it from their accounts...).