Replying to I really fucked up, advice would be great

Guys.. I really fucked up today and now i dont know what to do.

So last night I was working on a french project with my buddy and a friend of mine sends me a quicktime movie of her socials project over msn and asked me to convert it to wma for her, so as a joke we thought it would be funny to splice a 5 second porn clip on the end of the movie and send the converted copy back to her. I was planning on telling her about it if she didnt notice it, but the next day she tells me she wont be using the clip, so I didnt bother letting her in on the joke.

So afterschool..... a buddy of mine from her socials class runs up to me and tells me that her group presented the movie in class on the projecter and everyone saw the porno.. including the teacher. Now she is so fucking pissed at me, and so are many of her friends.. the thing is i didnt mean for it to fuck her over like this. I tried to apologize and offer to fix it and help make her project better, but she just blows me right off now.. have I really screwed myself over?