Layers, why do they always screw up?

OK, so I wanted to get layers cut in my hair that was about 4 inches below my bra strap, but only one legnth. I rushed and made an appointment at just a cheep salon at the mall cause it wasn`t like it was gonna be hard to cut layers in hair, and I wanted to get it done before my dance. So I tell the girl I want to keep my length but get layers, and she seemed to not think this was possible. She said it would be a little shorter with layers and gave some dumb explaination of why it had to be. But she said it would not be much and that my hair needed a little trim to keep it healthy.
So she started to cut and the layers weren`t loking too bad, although some of them were a lot shorter than expected. I saw them getting pretty short, but I figured she knew what she was doing and I wanted it to look a little different, that was the point, so I didn`t say anything. I was nervous then when I realized that she seemed to be cutting the ends off a lot shorter than I expected, even shorter than what she told ne she wanted to do. So finally I asked her and she said she was just getting done and that I should trust her it would look great.
Well after taking a very long time cutting, she put my chair down and showed me the back it in the mirror. I nearly jumped out of my chair, although I figured something was wrong. My hair barely reached my shoulders while still kind of wet, and some of the layers were above chin legnth. It is OK, but I cant even think about putting it all up. And she cut way too much off. I havn`t had hair this short since I can remember. Oh well though, its not horrible, but whenm I say keep the legnth, and someone cuts 8 inches off, something is wrong.

Sorry you had to learn the hard way as I did. My mom always trimmed my long blond hair that I wore down to my waist, even straight across since I was a child until I was in my mid teens. It was full, shiny and I always received alot of compliments from the guys. My girl friends were the ones always telling me to get it cut and try something short. Well one day, I decided to go the salon and try some layers as you did. I didn`t want to lose all my length at once, so I told her to take off a few inches and do something with the ends. Well this razor happy women chopped my hair to above my shoulders and it looked chewed. I cried for weeks and there wasn`t much I could do with it. It has been three years since then and I have not been back to a salon. My hair is now to the bottom of my bra strap and my boy friend trims the split ends for me. He is the only one I trust near my hair with scissors. I am growing it out to where it was before my haircut disaster. I learned my lesson big time. If your hair looks great long don`t be fooled by the hard sell to cut it. If I never see the inside of a salon again in my life it will be just fine by me.