Dummy's Guide to Countering Brigitte:
1. Hack her as Sombra. This shuts down all of her abilities with exception to her primary fire, and it turns off her healing and her shield, as well as interrupts/cancels her ult. It's an instant and complete shutdown. And then you can gun her down from a distance.
2. Junkrat, Bastion, and Pharah do insane DPS and landing shots on her shield is easy. Eat her shield and she's a sitting duck. Bastion's sentry is immune to knockback and stuns, Pharah can't be hit by her and her flail whip is easy to dodge, Junkrat gets more dangerous the closer he is.
3. Doomfist's charge attack ignores Brigittes stun and stuns her instead, or just straight up one shots her. Not to mention a single upper cut and seismic slam can knock her out of position, putting her at an extreme disadvantage.
4. Stay far away from her, and dodge her fail whip which is super easy to dodge anyway and has a cooldown.