Gap Kids sizing - is it quite big fitting?

[Pinkkahori]

Wanted to order a few things for 8 year old dd. She is a slim child but when I measured her the best fit seems to be an XS which is for age 4-5.
She doesn't seem that tiny. Surely the skirts and shorts will be way too short if I have to size down that much.

Does anyone buy kids clothes in Gap? How do you find the sizing?

Ordered last week. My son is 5, I ordered S which I think is 6-7. The jumpers exactly as I would expect and are slightly too big.