Fastest way to loose weight?? [for a 13 year old]?!

Fastest way to loose weight?? [for a 13 year old]?

im 5'3" and weight 115 lbs.
i want to loose at LEAST 15 pounds before july 21 because i am going to the beach with my bestfriend & all her family.
what is the fastest way to loose weight? i cant go out and exercise because during the day i am home alone & not allowed to go outside cuz of kiddy touchers.
should i just eat alot less?
should i do like situps during the day?
i really want to loose at least 15 [i really wanna loose 25] & get some abs.
i cant go get weight loss pills that will help me loose the weight cuz my parents think im rediculous for wanting to loose any. yet; then always make fun of me & call me fat?
[i dont even know how much to loose before i loose too much. how much should a 5'3" 13 year old weigh? cuz i wanna weigh less thaan that!]
&im not concerned about the healthiest way to loose it, i just wanna loose it as fast as possible

please help me!

First of all, you are a bit ridiculous for wanting to lose weight. I'm not trying to be mean by saying that, it's just the truth. You are the perfect weight for your height. If anything you are a bit too skinny already. However, if they make fun of you and say that you are fat, tell them to shut the f*ck up. Seriously, I think that if they are going to do that then you are perfectly justified in showing them a little disrespect. How dare they belittle you and ruin your self esteem?