Her dolls are (Asian) Ball Jointed Dolls, typically abbreviated to ABJDs or BJDs. The "original" BJD company, Volks, has two US stores- one in California (I believe San Francisco), and one in New York City, New York.
Some international sellers sell their dolls on eBay, but you can find a great deal of nice secondhand dolls on Den of Angels, as well as other BJD-related things.
Just be prepared to shell out a bit of money if you're interested in buying one, though- depending on size, whether or not the model is limited, etc., BJDs can range anywhere from two hundred to several thousand dollars.
Hope this helps, and there might be some more information in her Doll FAQ if you're still interested. Hayden's a Migidoll Ryu from, well, Migidoll.