No, we’re not referencing the song by The Cure. This issue came up a lot with my live-in girlfriend at the time. When I say “Let’s go to bed” I mean what I say. However my (ex) girlfriend used to always get angry at me when I’d actually fall asleep even though she was talking at me. The solution to such a problem is to stay away from the vague generality and stick with something more simpler like “Let’s go to sleep“… though the best way I was able to combat this situation and follow up argument is to simply not go to bed at the same time.
Just let her go to sleep first while you finish reading, or watching Netflix or playing videogames or whatever. Then slip into bed so you can fall asleep quick and painlessly without having to mutter as your drift off to slumberland.