I just don't see it that way at all.
I think (Pure guess by the way) that maura was making an attempt to free herself and get out of dodge at the time the SBD approached the accident.
When he approached, she had to freeze her exit plans. I don;t think at anytime whatsover that she was afraid of the SBD.
But in no way would she want him to get the police out there, she would be screwed royally. They would come, she would likely get locked up and very likely her father would've been notified and her whole plans (whatever they were would've been squashed).
I think she fed that story to the SBD, in hopes he would just leave the scene and let her be.
i think she quickly realized, especially when he went to his house which was just a little ways down the road, that she had to get out of dodge on foot and abandon the car because the cops were coming.
I think its highly telling, that she took alcohol with her but left her clothes and valuables behind.
She also had to know that her time-frame to escape (not just neccesairly to go commit suicide but whatever theory you want to believe she was in that area for) was working against her at that point.
By abandoning her car, she had to know that her gig would be up sooner rather than later and that it would get back to her father and family.
Why would she buy snacks and bring her stuffed monkey and jewelry on a suicide?