I have a plan to get the misses covered in chocolate, like chest down to upper legs, other than the sheets getting chocolate on is there anything wrong with doing this?
There are a lot of complications that could arise from this. Potential for yeast infection for her, potential bugs (ants and/or roaches) coming into the room, the extreme stickiness of it. I don't highly recommend this.
Its not going to be masses of chocolate, just small bits like hand prints on bodies etc, and sheets will be washed next morning anyway, yes she is okay with it
I would say as long as your mattress is properly protected and you plan on washing the sheets the next morning then there should not be a problem. Another fun thing to play with in bed is shaving cream I have emptied several cans on the bed and covered my self and then climbed into bed and had lots of fun.
Heck yes, there is all sorts of wrong with all of that - I will try to be brief:
1) Not nearly enough coverage... go all in! Head to toe!!
2)... sleeping or 'sleeping' ? If you're 'sleeping' (wink, wink, nudge nudge) then go for it, just clean up good afterward. If you're actually sleeping as in Z-Z-Z-Z-Z... then I guess you can, but sort of wasting the experience, no? Like sleeping through a rock concert, fireworks show, etc...sort of missing the best part. Though I guess something to be said for the experience of waking up covered in chocolate and ready for whatever happens.
2a) If actually sleeping, know that the chocolate might tend to seep through sheets more than you'd think. Over time it may actually pull moisture out of the air and become more liquid... so I'd probably go with vinyl sheets as suggested.
2b) Anytime, I've fallen asleep messy, I usually wake up cold. Falling asleep with any sort of liquid really seems to pull heat from the body, so you'd likely want the room warmer than normal, or have blankets / extra sheets to pull on. ie - I thought it would be fun to sleep muddy one time, but woke up freezing... and that was an 85F summer night... though having an extra body might have helped, too.
Love you, too
Maybe not sleep in it overnight, you may not like what you wake up to. 
? If you're 'sleeping' (wink, wink, nudge nudge) then go for it, just clean up good afterward. If you're actually sleeping as in Z-Z-Z-Z-Z... then I guess you can, but sort of wasting the experience, no? Like sleeping through a rock concert, fireworks show, etc...sort of missing the best part. Though I guess something to be said for the experience of waking up covered in chocolate and ready for whatever happens. 
