The scientific problem with women growing is that when you double the size, you quadruple the strength and you
octuple the weight. It gets out of hand very quickly.
Then there's the matter of breathing. Your lungs are made to absorb oxygen molecules of a very specific size. A 50' woman would be literally incapable of respiration, no matter how much air she inhaled due to the oxygen being far too small to be of any use. The opposite is also true - a shrunken woman would also find herself unable to breathe because the oxygen would be too large to be absorbed properly.
Then you get into the whole "how does she eat/drink/whatever" questions and the whole thing just dissolves into impossibility.
That's why I prefer magic as well!
