When I was a boy, I was taught a simple formula for converting imperial to metric: double it, then add 30. So for example 10 degrees celcius is 50F (10*2+30). A case of Molson Canadian beer would be equalivalent to 54 PBRs (12*2+30).
So to convert imperial to metric, you would just do the opposite - subtract 30 and divide by two. That puts your fair lass at about 67" tall and 10 pounds, A bit thin for me, but YMMV.