You can’t lose 25lbs in any healthy manner. That’s too extreme of a weight loss for someone who already has a relatively healthy weight.
Not to mention 3 hours of gym time sounds like a major burn out after two weeks… followed by a major binge. And what happens when school starts and you can’t go to the gym for 3 hours anymore? Hello instant weight gain! You’ll go from the “wow you lost so much weight” girl to the “wow I didn’t think gaining so much weight in such a short time span was possible” girl.
Don’t screw yourself over like that. Don’t put yourself in a vicious yo-yoing cycle. Do it right the first time around. Take it slow. Aim to lose about 1 pound a week. It is practical, and you’ll be able to stick with it without driving yourself insane. You’ll be more likely to actually keep the weight off in the long run if you develop healthy eating habits (not just an 8 week diet plan). And you won’t run as high of a risk for disordered behavior.