this absolute stuff is rather irrelevant.  what you need is a relative scale.   3d is vector with another dimension- scale is whatever you define it to be.  what's important is relative dimensions. 

a few of the women at my work are very, very petite.  as in considerably shorter than i am, and i'm 5'3''.   none of them seem to have large heads, imho.  i think you might start looking at a few references, find one or two you really feel fit your character, and making charts of proportions according to head heights.  and don't use stars.   not only are they not the norm, the pictures of them tend to distort and flatter.  there's actually a famous picture of kate winslet from a magazine or something where she's in front of a mirror.   apparently someone decided she was too chunky and photoshopped about 20 to 30 pounds off her, mostly in butt, thighs and waist.  but they forgot to take care of her reflection, which was rather small and in the background.  it's kind of a funny picture if you know what to look for, but also telling because the edited version looks perfectly natural. 

there are lots of artist references out there- i suggest making use of them.