I’m an 17 yr. old girl who is 5’5" and 140 lbs., medium bone structure. I generally eat healthy (no soda, snacks, etc….) but have recently restarted a daily exercise routine (I stopped after a long vacation in the winter). I’m planning to swim 2x per week, take ballet lessons 2x per week and lift weights 1x per week (1 hr. each). Is it possible for me to lose 15 lbs. by the end of the summer? or is 140 lbs. a healthy weight for me?

find calorie/fitness calculator on the net, enter all your stats and it will tell you how many calories you need a day to maintain, take off 300-400cal off that number and thats how much you need to lose.
eat 5-6 small meals a day (eat every 2-3 hours)
5-8 servings of fruit and veggies a day
8 glasses of water
have complex carbs for breakfast – they give you energy
have lean meat (protein) for dinner – repairs muscle
cardio exercise 4-6 times a week for 30-50min, light weight training
dont consume foods that are made of white flour (white bread, cakes, past etc.), sugar loaded foods (cookies, icecream, candy etc) and nothing fried, oily.
ofcourse you can spoil yourself once in a while with a little treat:)