Apparently the one she used to have was slow at publishing the books, and has subsequently gone out of business. The last two books were published in the US this year, if I can trust my googling skills, and they have been available from harper collins for... years, I believe.

Lack of availability is probably one reason it is hard to find in the US, and another aspect is likely that if the publishers don't care to publish quickly, they are somewhat less inclined to promote the books too.