I did something bad and now I feel really guilty.

A few months ago I did something really bad. I listened to one of my friends. She begged me to do something I didn't want to do. At that time she was miserable, crying and eventually I did it. I am not proud of it. A few days later the girl that I did this to found out, but she doesn't know that my friend made me do it. She doesn't know that because of me and my stupidity she feels that way. The problem may seem minor to other people, but it seems huge to me. I am a teenager and I have 2 more years in highschool. I just got close with most of them and now I don't want to lose them! I feel terrible, I prayed, I cried, but nothing makes me feel better. I can't confess to her, she will never speak to me again. I lied to her face... How could I do that? And now I feel miserable because of my friend. Yes, I am guilty too for doing it, but at that time she made me. She couldn't do it herself, because she didn't have the guts. And now she is completely calm and I am dying inside... Please, help me. What can I do to make things right? I don't want the girl to find out, she will never look me in the eyes again and so will my classmates. I feel awful.