My dog is aggressive on a leash, and I don't know what to do. She becomes fixated when she sees another dog on our walks/runs and barks/lunges at them. I've tried having her leave it, sit, face away, etc. I've tried distracting her with treats. I've tried giving gentle tugs to redirect her attention elsewhere. Nothing is working. We did a training class with her, and she picked up on everything else well. But this one quirk is proving challenging to get rid of. Any suggestions are appreciated!