Thirteen is a hard age. I don't have experience with prozac, but I have experience with 13 year olds in the family. There is a lot of pressure at 13. Pressue to be popular, pretty, cool, wear this, do that. Similar to what we went through, yet different. More. Younger. When my brother was this age he want from doing well to do REALLY poorly, not turning in homework,etc. My mom wondered if he was on drugs and yanked him to a psychologist so fast he had whiplash! Turns out there were two things going on. 1. his grades - his 3rd period teacher insisted that all homework be turned in before the start of the school day or it was considered late. He didn't feel like walking across the school in the morning to turn in his homework, he wanted to hang with his friends, so his homework was late or wasn't accepted. Grades went down. 2. bully. There was a group of boys that were picking on him for being smart. Kicking his heals, pushing, dropping his books, etc. He knew if he got in a fight that he'd be in trouble at home, so he just took it, and became depressed and angry at home. When my Mom/Dad found out they were shocked. They didn't want him to fight, but defending himself was different. As soon as he was given that green light, he defended himself only once. The kids were so shocked to see that he wasn't a wimpy geek that they started leaving him alone. He came home that day estatic. Things quickly went back to normal.
Another post suggested being more active in church, which is good,and I agree with, but youth groups in church can be very cliquish. If you're not one of the popular ones... Does your daughter have any interests - music, painting, running? Perhaps if you help her find strength in something outside of school and church that she likes, feels good about, then her attitude will improve. My son just started taking Tae Kwon Do in Woodbridge. There are many girls there. I think its good becuase TKD is an independent thing that each person can strive at and there is no pressure to be better than someone else.