Agatha KNEW All Along. She could've told them at any point and saved lives, but she didn't. It was Wiccan making the reality, but she knew nearly instantly he was making The Road real because she knew it was fake. She was playing off him to succ some witch power from whoever she could. She could've saved several lives, but she purposefully didn't even attempt it because she wanted power back.
It is funny that Sharon fucking died for no reason and Agatha keeps going "WHO?" because she really was a nobody bystander who got murdered. I was wondering if they'd do some "nah she's alright!" or "non-witches can't die on The Road!" or some shit, but nah. Gardener lady is dead.