Davis said Maxwell was more like a brother than a cousin to her, and that she had just seen him Friday morning, when they saw off their cousin, Bernard, who was heading to prom.
Maxwell said they should have a barbecue for Bernard that night.
His last words to her were, "I love you, be safe."
"I don't know if he felt something was going to happen, or something was wrong," she said.
Davis said Sunday she hasn't been able to drive since Maxwell's death.
But Saturday night, Davis said, she had a talk with her cousin.
"He came to me in a dream and said, 'I'm OK. There's no reason to be scared or sad,'" Davis said. "All I could do was just smile. I knew he was OK."
Devante Barbee, 19, said he met Maxwell when the two took a tour of Morehouse College in Atlanta as high school juniors.
"He always did the right thing," Barbee said. "He always stood up for what was right, and that's exactly what happened the moment he got killed. He got killed standing up for what was right."
Barbee said the death of his friend makes him glad to be going to school at the University of Illinois at Urbana-Champaign, far away from Chicago's violence.
"This city's too much," Barbee said. "It was a family get-together. All he did was ask people to leave the party."