Fluff- silk long underwear for tall, plus size woman

I can't seem to find anything fitting this category. I bought DD a pair from Lands End, just the regular XL. They are about 6 inches too short, and a little bit too tight. She'd like to size up just a touch (if I reordered from there, I'd probably try the 1X or XL plus, whatever they call it, but they don't do tall in the women's underwear), and of course, find some that are actually long enough. But I can't seem to find any anywhere. She sometimes goes with men's sizes for jeans and all, but the men's long underwear is cut for, ahem, men. It doesn't necessarily have to be silk, but we want something very thin and light and not overly hot. Thanks!