Teen fat loss

Hello, I'm a 16 year old girl. I have extra fat on my buttocks and stomach. My BMI is 19.5 which is completely normal, but my body fat percentage is 24.1%. My parents were really skinny at my age, so was I until I became a teen and started to eat junk food, my lifestyle was and still is sedentary, but this hadn't have an effect on my figure till my teens. I've been eating healthy since last summer, but it didn't have any effect on my fat, I started to eat junk since last two months, still no effect on my body. So I guess not diet, but exercising is the one to be blamed for my problem. I was walking for 2 hours everyday, but still without a result. I then found out it doesn't burn much calories. I want to have a body like that in this image, I don't want to have bulky shoulders or six pack.
Which exercise should I choose? Is swimming a good option for quick results? Like 1 month.

by randomstrangere via Bodybuilding.com Forums - Female Bodybuilding