how many calories is enough?

 For a while, I ate 1200 calories and lost 20 pounds. Now i'm trying to eat 1200 calories again, but I get so hungry and cannot stop thinking about food. I'm a female and 17 years old and 5'9". I'm running/walking every morning for about 45 minutes and I dont want to starve myself.

 Would 1500 calories be ok? I want to lose 20 pounds and plan on working out more, like going to the gym and getting toned.

I'm also a vegetarian, so what would be some filling foods that have a lot of protein?

 How long will it take my body to adjust to the caloried deficit?

http://www.bcm.edu/cnrc/bodycomp/bmiz2.html

Check out this link aimed especially at the under 21s.  If you enter your stats (150lbs 5'9") and read off the number associated with 'moderate' activity you'll see that a) You're already the perfect weight for your height and b) how many calories your body needs to be healthy.... 2610 per day

So 1200 or even 1500 is a complete non-starter... no wonder you're hungry!   And 130lbs is an unrealistic target weight.  If you really wanted to lose a few pounds you should aim for around 2000 cals a day and do some exercise to tone up.   140-145lbs would make you very slim and healthy.  Crash-diet and all that happens is that your weight yo-yo's up and down... often ending up higher than where you started.  Which is what you found last time and it's known colloquially as 'dieting yourself fat'.

Protein-rich vegetarian foods are things like tofu, eggs, beans, lentils, chickpeas, nuts, seeds, dairy products, quinoa grain.... lots to choose from.

Thank you! This has helped a lot.

I don't know much but I think you should up your calories to 1,800-2,000 calories and see how that goes. Some protein foods are

 dairy products like low fat cottage cheese, eggs, nuts, types of oats like granola bars, oatmeal, and a lot more.