Gardy vs Gardy

[Aggy&Co.]

We all know the text on Gardevoirs Bring down. Say there are 2 active Gardevoir with an equal amount of damage and no bench pokemon on either side, Player A says I'll use bring down to knock out Player B's gardy. Player B says you can't because the attack says Choose a pokemon except gardevoir
The attack is self referencing but it still says "except gardevoir" and there is no distinction between Gardevoirs.
Who gets knocked out or is the attack completed?

 

[PokePop]

Self Referencing means the Pokemon with the text printed on it only, not every Gardevoir in play.
Hence the "self" part.
The opponent's Gardevoir would be Knocked Out.