They come up a little large like most of their clothes.
On the ones linked, the leg elongator, I have a mid blue pair from last season which I wear to death, and they fit perfectly and are a 27, a little snug, so very flattering, due to the cut. However thats unusual they are true to size.
I ordered the darker indigo distressed wash ones now on the website, in a smaller size, as I could see on the model last year the paler ones were tight on her and pulling, and on this model they were loose so I ordered the 26, but they are maybe a bit too loose, too much material round the tummy, and too big on the waist, so am trying the 25, for comparison, I’m an 8, but I need to wait for them to be delivered, then will decide which to keep. As I’m a little undecided.
I also have long legs, I’m five six and a half. and their trousers fit me perfectly leg length wise, and I’d say the regular length is perfect at 32 inches. I also noticed this years have a slightly narrower flair than last years.
so the way I do it is look at the model and see how it fits on her, they are typically an 8 and if it looks loose, then irrelevant of your size, size down, and if it looks snug, stay at normal size. Alternatively order both sizes and return the one which doesn’t fit as returns are easy, that’s basically what I’m doing this time, I’ve ordered both then will return one pair.
the jeans are fab though, they hold their shape, very very flattering on, and soft.