Why a body double?

For her walk of atonement it made no sense for her to have a body double. Lena is an attractive woman for her age and should not need a body double. For five years Game of Thrones has been known for showing women naked and this should've been known by an actress who's been a part of the show since the very first episode.

For Lena to use a body double seems cheap and cheating. The only thing I can think of is Lena is uncomfortable with her body but like I said, it makes no sense because now unless people actually do research, they'll never know that wasn't Lena's body so what's the difference anyway? She should've just sucked it up and done the scene properly which would've given us an even better performance.