Thats great Maria, I have noticed that some charts vary slightly.
Carley, there is a way to measure body fat more accurately than using a BMI charts, you go to the doctors or a gym and get them to measure your skin folds with calipers or use Hydrostatic weighing (underwater weighing) it's the most accurate way to calculate body fat - that is, if you can find a hydrostatic weighing tank.
I myself prefer to use this method.
When we think we are slim the real way to tell if the charts are off is to have a photo taken of ourselves wearing a clingy top without an over shirt or jacket that will conseal our blubber.
If it shows we look slim, then our hearts will be healthy and won't be taking on any more strain.