Is there anyone that can teach her how to sew? I LOVED making my own Barbie clothes. Barbie patterns can be bought at places like JoAnn Fabrics, but look online for free first. Remember you don't need lots of patterns, because the variation will come from the different fabrics. You just need the basics: dress, pants, top.....
I totally taught myself how to sew, just by looking at the patterns and giving it a try. I taught myself how to use a sewing machine and hand sewing the same way.
Some will say that sewing clothes is expensive, but it does not have to be. First ask your friends if they know anyone who has leftover fabric. Chances are someone knows someone. Next go through your own clothes. You can cut apart old stuff and make really cute little outfits out of things you would toss or not wear anymore. And you can skip the hemming of the tiny clothes by using the hemming that is already done on the regular size clothes.
The big cost is velcro, but that stuff is golden for getting those little clothes to stay on.
Sewing tiny is not as hard as you may think. The key is to think "outside the sewing box." For instance you hem the cuffs on a sleeve BEFORE you sew in the sleeve. You do not turn it up and try to sew it once it's closed and itty bitty.
Same with the hems. You sew them before you put the pants/skirt together.
Something else girls like for their Barbies is odds and ends of "trims." Little pieces of ribbon become belts, hair bows, and even little tiny tops. Your Barbie lover will just tie them on,nothing fancy, but fun for her.
They also like pieces of fabrics, just a rectangle of pretty fabric. Old camisoles and nightgowns are perfect for this. They will wrap them around the Barbie and turn them into dresses, skirts, head wraps. You will be amazed at what they can do without any sewing involved. It would be fun just to put together a box of "stuff," that has no sewing whatsoever. Again, skip the fabric store and hit Goodwill or an inexpensive resale shop. For 25 cents you can get really cute stuff. And don't forget little dried or plastic flowers.
The one thing I would splurge for is Barbie shoes. I saw a package of them at Meirs for $10.00.