Okay, So I told my youth leader that I'm anorexic and she said she's gonna have me step on her scale on Tuesday (TODAY is Monday) and she said I need to gain weight by eating 3 meals today and tomorrow and if I didn't gain weight then she's gonna have to tell my parents. So, how can I "gain" weight? Like drink a lot of water to gain water weight?? Or what? How can I make the scale say I'm heavier then I am? (No lectures, it's not going to help anyway, I'll just ignore them, only answer if you're going to answer my question.)

Sorry - this isn't what you want to hear but I'm going to tell you anyway. Feel free to ignore.
She didn't do the right thing. The worst thing is to tell a person with an eating disorder that "i'll tell on you if you don't gain weight". Now, you're turning to deception to hide the fact that you haven't gained weight - this only alienates you more. Eating 3 meals isn't going to show any dramatic weight gain anyhow. Plus, asking somebody with an eating disorder to just "eat normally" is outrageous.
I feel and for you because I've been in your position - but your parents need to know what is going on with you. When they find out, they can't force you into recovery, so it won't make a huge difference whether they know or not, but still - you need to have as many people in your corner as possible.
Again, I know this isn't what you wanted to hear. But you DO have the right to tell her you don't want to step on the scale. It's traumatizing, and the fact that she is holding this over your head about telling your parents is very unfair. She cannot forcibly weigh you. Explain to her that you told her because you trust her, and want her support - not because you're necessarily ready to recover. You're going to have to advocate for yourself a bit.
Good luck.