"I just wanted to make sure she was OK," Alsop told "What Would You Do?" anchor John Quinones afterward.
"She could have a seizure, she could throw up, and choke and die, she could be raped," she said.
And it wasn't just Isabelle Alsop who took action. As soon as Jillian appeared to be in trouble and the teens' drinking appeared totally out of control, other people either called the police or directly confronted the group.
Abigail Harris ran across the street with her young daughter when she saw our actress fall onto the sidewalk. Harris jumped in the guys' faces, grabbing the beer cans out of their hands.
"You can't drink," Harris exclaimed before grabbing hold of our actress to make sure she was okay.
When John Quinones asked Harris if she was worried the guys might turn on her, she laughed.
"They're young kids," she said. "I wasn't scared for my life. I was scared for the little girl."
Harris said she felt it was her duty as a mother to step up and stop the underage drinking.
"That's just being a mom, and a concerned adult," Harris said.
Watch the scenario unfold Friday at 9 p.m. ET on "What Would You Do?"