Your drawing is technically fine, but speaking about constructive criticism something could be made better:

the detached head should be a bit bigger because of perspective and because it looks better that way ;)
the expression on the head also should match what she is saying
In the fist picture if you say she is nervous it would be better to make her eye look right-up or down to show that she is nervous-shy.
On the second picture, maybe some ahegao expression would be appropriate.

I personally think that free head would look better than head stored in the glass tank, it also needs a bit more attention ;)

The idea is interesting but just one picture is a bit waste of effort if it has no story behind it
so you may consider adding more story to it which will make everything far more enjoyable.