The speaker was nervously anticipating something. This is a three-fer mashup I think. “Champing at the bit” and “biting my nails” both meaning to anxiously await something, are clearly in the mix, and also “bites the dust” (to die) is in there. Perhaps the anticipation was so exciting that she thought she was going to die? In any event, a big thanks to Katie Mroczek for uttering this one and sending it on, with the help of Anthony Kovacs.