I had an near -exact- same whisper once also resulting in a ignore.

Except I attempted to explain what I was doing after she ignored me from another character, to which the person replied "Oh my god! You knew I ignored you yet you go around it by whispering me with another account! Reported for abuse!"

So I just just "Ahem... You knew I was multiboxing, so I believe it was you who failed to ignore all my characters in the first place. ;p"

After that I couldn't bother anymore with it as it was clearly starting to go downhill. :P But yeah, some people are just -so- stubborn!