Sure, Grace can shrink more. Why not?
Literally speaking, Grace is correct. Being 1:2 scale means everything else is effectively 8 times bigger.
I've seen some debate on how one would literally perceive the world at that size, but I personally think everything would genuinely seem 8 times bigger. Between using one's self as a frame of reference, all of our various senses, our eyes being scaled with us, etc, it makes sense to me.
Of course, a person actually being that small with those proportions would come with other issues if we were talking realism, so really, the answer is "everything seems 8 times bigger because magic says so, nyeah".