Help, I'm in the worst situation ever!!!?

Last weekend I was bored so I asked a few friends to go to the mall, including this girl i really like, Vivian, planning to ask her out at the mall. When I got there and met up with her I saw she brought her best friend, Rachel, who goes to my school. Rachel is the weirdest girl ever, and really isn't that good looking. When it seemed like the perfect moment I asked out Vivian and Rachel just yells yes think i asked HER out, and Vivian is all excited because its her first boyfriend so i couldn't just say I meant Viv right there or she would never go out with me. I waited to go home to call her and explain it to her but i got an email FROM HER DAD saying stuff like her was in the army and i better not mess with her or break her heart, so now i cant just call her and explain. Ive tried everything to get her to stop being attracted to me: telling her I smoke weed, i watch , i don't plan on going to collage, spelling everything wrong when we text and IM each other, being obnoxious and perverted, but nothings working!!! And I told her to keep it quiet but shes telling everybody, WHAT CAN I DO??????