You may not be surprised that the answer is:
that depends...
But truly it does! How much you should eat depends on many factors, most importantly being what the outcome is you're working towards. Typically that falls into one of three categories:
Maintenance: a rough estimate for daily calories is your body weight x15, however age, gender, and activity levels will all impact this number.
Deficit: typically 200-300 calories less per day than maintenance (or your body weight x11 or 12). It's a good idea to have a range here, rather than an absolute number.
Surplus: shoot for about 10 - 20% more calories than maintenance if your goal is to gain muscle size and strength.
(For more precise calculations, and a full, personalized nutrition guide, check out my Custom Nutrition Calculator.)
What do these calorie ranges mean in terms of food?
Active women do best with 4-6 servings of each food group per day (~1,500 - 2,100 kcal):
1-2 palms of protein-dense foods at each meal
1-2 fists of vegetables at each meal
1-2 cupped handfuls of carbohydrates at most meals
1-2 thumbs of fat-dense foods at most meals
Once you have determined your target range of calories (or servings of each food group), be as consistent as possible for a few weeks. At this point you can evaluate your progress and decide if you need to adjust up or down.