I really cannot add anything to the advice you have received.

I know that you realize that you must take the major reponsibilty for this incident occuring given your knowledge of Indie's unreliable temperament and the fact that you did not pull out of your round when you could clearly see that she was wound up to the point of aggressiveness. However, some of the blame must also be laid at the feet of the trainer: (a) for not observing and informing you from the start that you need better ob, (b) for allowing a dog who is not under complete control at all times to participate in a sport that is highly exciting for the dog, and (c) for permitting you to go round with a dog clearly aroused to the point of uncontrollable belligerence.

Indie does not need socializing, she needs desensitizing. Steer clear of agility and go the behaviourist route. Kazz has extremely kindly offered to assist with an initial consultation, so get it underway asap.

Good wishes
SB