a friend of mine is accusing me of creating a fake facebook account how do i prove this wrong?

[valente788]

so someone on facebook has been contacting my friends boyfriend and telling him things about her only apparently i would know. it wasn't me though but she has made up her mind that it is and i don't know how to clear my name here, is there any actual proof i can come up with to show her beyond a doubt that i didn't do this?
well now my friend is threatening to tell people things about me that could get me into big trouble. she said she'll do this if whoever is contacting her boyfriend contacts him again. i am actually freaking out at this point because i have no control over when this person on facebook decides to contact him again and i still cannot convince her that its not me!