"She told my BF that I flirted with other guys!"

My BF lived two towns over, so I didn't get to see him very much. One day, I was at my BFF's house with him and his BFF (who's dating my BFF). I was whispering things in my boyfriend's ear, like "I love you" and stuff. My BFF heard me and made up a TOTAL B.S. lie and said "So why do you flirt with every guy in the school and not tell him about it?" -- RIGHT in front of my boyfriend. I was so mad that I had to leave right away. Thankfully, my boyfriend didn't believe her. But later that month, she spread two rumors that I hooked up with two other guys that got around to my BF, and he dumped me. I was so upset -- I haven't spoken to her in a year. But my ex is considering taking me back.