Louise is absolutely uninteresting because of this. Yes, it's a beautiful scene, but the script doesn't make sense. Well noted. Just a collection of pixels on the screen.
I understand that Louise/Jeremy/Lena scene made sense, since it was Louise's initiative, because she subconsciously understood what Jeremy is like and tries to diversify sex, make it more kinky, so that he doesn't lose interest in her. There was motivation.
And here - nothing. Ian is a barely familiar guy for Louise, and knowing what a prude she is - all this is implausible.
Eva was in a hurry with the release and poorly spelled out these moments, I hope they will be corrected in final.