In my mind, Jessica and the car was lit on fire very close to the time of the 911 call--maybe just minutes or moments before. I don't think she would have still been alive if she had been on fire for 15 or so minutes. Fifteen minutes is a long time to be in a blazing fire and still be living and conscious enough to speak or try to speak to first responders, and I do believe she spoke the name Eric before she lost consciousness. The biggest reason I believe this is that LE went to EB's house by 9:30 according to him. Keep in mind that this was probably the second time they had gone there because EB said they had called either his mom or his grandmother, and WENT to one or the other's house looking for him. I can't remember which one's house they went to, but this would have been BEFORE they found him at home at 9:30. So, they went looking for EB probably less than an hour after the 911 call. I can't think right now of any other reason they would have started looking for EB that soon unless Jessica had spoken a name that sounded like Eric or Derrick. Believing that she was conscious and spoke a name or names makes me believe that it was not before 8 o'clock that the fire was lit. I believe she was lit on fire some time between 8 and 8:13 when the 911 call came in. Any earlier than that, she would not have still been conscious.
We've read it both ways--that she was walking in the road on fire and then she was laying near the car and not still on fire, so we don't know which to believe. I tend to believe the first report "walking in the road on fire" because somebody had to have told her father that because he said it too, in his interview with a reporter. He would not have just made that up, IMO. I think the 911 caller saw something that we are not being made aware of. I think s/he might have seen a person or persons fleeing the scene and just couldn't identify them. All this is OMO except for the links to the interviews on the media thread.