Oh! I almost forgot one other very useful reference!
Wikipedia's Body Proportions page.
On the idealized body (not quite realistic, but close enough for most purposes) the body is divided into 8 sections. Verses a six-foot-tall guy (for reference), each loss of nine inches would cause a shrinking girl to drop one category in terms of where she measures up. Since the eyes are on the midpoint of the head, her eyes would be halfway down to the next category. For instance:
5 feet, 3 inches: The top of her head would be level with his chin. Her eyes would be a bit below his shoulders, I think.
4 feet, 9 inches: Her eyes would be about level with his nipples at this point.
4 feet, 6 inches: The top of her head would be about level with his nipples; her eyes would be a bit above his navel.
3 feet, 9 inches: The top of her head would be about even with his navel.
3 feet, 5 inches: Her eyes would be just about even with his pubis at this point.
3 feet even: The top of her head would be even with his pubis.
2 feet, 3 inches: The top of her head would only come midway up his thigh.
1 foot, 6 inches: The top of her head would come midway up his calf.
9 inches: The top of her head would be near his ankles.
If some of those seem off, it's because we're dealing with idealized and not actual body measurements (this is particularly visible in the last few)... but the general idea should be pretty close.
...geez, writing all that down makes me want to shrink someone.