*crazy theory pops into XwingRob's head*
Ok here's a good one.
Mia Campbell is becoming odd in the head. She is no longer believing that she is an actor who plays as Lacus Clyne, she is starting to believe she IS Lacus Clyne. So, using her influence, she entices a Zaft Commander to send a strike force to wipe out Lacus, so that she can become the only Lacus Clyne.
And BAM! There we have it! Just as Gundam SEED's psycho bitch was Flay Alstar, Destiny's psycho bitch is Mia Campbell.
She'll even try to seduce Athrun after learning that Cagalli was marrying someone else.