First of all, starving yourself is not the answer. If you do that, you may just end up gaining more weight because your body will realize it's being starved and it'll store fat easier.
Now then. If your mom starves herself, I'm sorry for her. She must feel miserable all the time.
That being said, I have to say, I know very much how you feel. When I was 14 last summer, I was borderline obese, and it didn't help me at all going into high school. I understand how you feel and where you're coming from.
Now, you're 5'3", so your ideal weight is somewhere around 120 pounds unless you have a very slight build. Saying that you'll never be happy unless you're under 100 pounds is unreasonable. To get there, healthy weight loss is 1-2 pounds a week- and don't feel bad if, sometimes, you don't lose weight, because that's healthy as well. Also count you calories while losing weight. If you're sedentary (not active/a little active) you should eat about 1700 calories a day, if you get about an hour of exercise you should eat about 2000 calories, and if you're very active (2 or more hours of exercise) you should be eating 2500 calories a day.
Cut out all soda and drinks except milk and water. You should drink 1 or 2 glasses of milk a day because you're growing (make sure it's 2%), and you should shoot for 6 glasses of water a day, 8 if you can. It's not hard if you keep drinking it, because you could be dehydrated without knowing. Water is also good because sometimes if you think you're hungry, it may just be that you're thirsty. And, make sure that you have a glass of water about 15 minutes prior to breakfast lunch and dinner- it'll decrease your appetite. Drinking water helps out your kidneys, making it to where your liver, which takes care of body fat, doesn't have to work for your kidneys, thus letting your liver work better so that it doesn't have to store fat because it can't get anything else done. Water also makes your skin look better.
As for meals, you should eat whenever your stomach starts growling and hurting. This means that you're hungry, and it's the natural cue for mealtime. In between meals when this happens, eat a piece or two of fruit, a cup of cottage cheese, a handful of nuts, or something else that's healthy. You don't need a lot because there's about four hours between meals and you won't need a lot to sustain you. At your meals, just control your portions. If you're eating macaroni and cheese, a large spoon should be enough, for example. Just pay attention to the serving sizes and how much you can eat. Do not eat fast food- it's nasty, it's terrible for your whole body, and it makes you feel slow and sluggish. You can eat a lot more of the healthy stuff than the junk food and sweets. Also, you can eat if you're hungry after dinner. A midnight snack is fine as long as it's healthy- you won't gain weight if it's a grapefruit, but beware if it's a cupcake!
Also, you should be getting an hour's worth of exercise a day.I'd recommend jogging, since it gets rid of fat on your entire body instead of a particular area, but if you're not up for that at the moment, start with brisk walking. If you live in the city, try walking a block twice, or if you live in the country walk a block once. Join a school sport, buy a bike and ride it around, play with the family dog, go out and swim, whatever is fun and works for you. If you keep making yourself do this, you'll come to find that it's really fun to be outside and have a good time while getting exercise. If you're doing something you think is boring, like walking, get an iPod and listen to music while you're on the treadmill. Just stay active. And remember this: What someone says is a great workout for them may not work or work the same for you. Jogging, playing basketball, and riding my bike are great workouts for me, but they may not work the same for you because you're not me- maybe swimming, volleyball and yoga work better for you. What I'm trying to say is you need to find what works best for you and your interests.
Remember, there's no shortcuts to a healthier body. Starving yourself begins to work until you kill yourself, diet pills work until you stop taking them, and fad diets work until you decide you're fine without them. The best way to lose weight (and be a healthy person) is to live a healthy lifestyle.
Good luck. If you want to lose weight, you can.