Are 1800 calories enough for a female?

I'm 50 kg, 162 cm, 17 years old.

1800 calories isn't too little for an inactive person, especially if you are overweight. It's the combination of what you consume and what you burn that makes the difference. When you consume 3500 calories more than you burn, you gain one pound. Likewise, when you burn 3500 more than you eat, you lose a pound. Your answer depends on the amount of exercise you get.