Jackson is the only alleged participant being tried this week. Bakr and the three others are being tried separately.
Bakr told the jury Thursday that Jackson was in charge the night of the murder.
Jackson "was supposed to go get money from the guy who owed him for drugs," Bakr said, adding, "They were going to rob" DeGennaro.
If DeGennaro did not give Jackson the money, she said, others would "hold him at gunpoint."
She drove one of the two cars the group took from Trenton to Levittown, then waited in her car while Jackson and two others left to get the money, she said.
Bakr, 17 at the time, said she had been drinking rum that night, but was not drunk.
A few minutes after Jackson exited the car, she said, she heard gunshots. Two of the other alleged conspirators - who had originally driven in the car trailing Bakr - ran to her car and urged her to drive off. She drove back to the parking lot in Trenton, where Jackson had arrived in the second car, she said.
During cross-examination, Jackson's attorney, Craig Penglase, pointed out that Bakr lied about her involvement to her family, friends, and the police. Bakr admitted that, but said she was telling the truth on the stand.
Penglase also focused on Bakr's saying one of the shooters put a black gym bag into her trunk before leaving for DeGennaro's home.
Bakr told prosecutor Matt Weintraub that she thought drugs were in the bag, so Penglase asked whether she believed at the time that they were heading to a robbery with a bag full of drugs, not guns.
She said that did. The bag contained the shotgun used to kill DeGennaro.
The trial continues Friday.
Contact Chris Palmer, 609-217-8305, email@example.com, or follow on Twitter, @cs_palmer.