To start with, your original post had me scratching my head. Makes more sense now with the subsequent explanations. To be clear, you have a 7 year old girl who is permitted by her parents to visit her 20 year old neighbour after he returns from juvenile detention for strangling his brother to death, is attacked and almost killed, whereupon her father kills the neighbour and deserts her. Can't imagine where the trust issues arise? To top this off, she enters a serious relationship at a very young age ( make him a jock, or the calmest human being on the planet, for effect) and then he departs by dying. Any one of those elements, in my opinion, is enough to leave a mark. People adhere to worldview, including distorted worldview, as protective measures. The 7 year old her won't, probably, be able to articulate the trauma, may do so at a superficial level as an adult, but those scars go deep and manifest in behaviour. Therefore, important to show and not tell. Severe trauma, in my opinion, doesn't particularly need to be repeated to have impact. Every day daddy stays away repeats the abandonment, in any case. Best of luck with it.
DISCLAIMER: The following is not a commentary of "real life." People deal with trauma and react to trauma in many, many different ways. And not being a mental health professional myself, I can't speak for the direct cause and affect of a person's trauma and their reaction. What I am speaking about is "the good story" rule, which doesn't always mirror real life, where causes and effects are more defined for the sake the story, even if that cause and effect isn't 100% realistic. ********** Such a traumatic event would only create an issue of trust if the person who did it was someone she actually trusted. Like a parent or guardian. That's because the person who victimized her created the misbelief by challenging the safety of trusting others and thus she flips her belief. This is why rape is such an often terrible crime. Because it's usually perpetrated by someone the victim knows. And while the victim may not particularly trust that person with their life, maybe they were just an acquaintance, they at least trusted the person not to do that. If this was just a stranger, then it wouldn't have that same affect. At that point her misbelief might be going out at night. Or she might wear her shoes to bed in case she has to get up and run. Or she might have a mistrust of police, especially if they victim blamed or weren't particularly helpful or sympathetic or outright didn't believe her. I guess what I'm saying is I don't see the direct line from the trauma to the misbelief.
For the average person - holding on to one horrible event that happened to them as a child and allowing it to completely derail their ability to form healthy relationships as an adult is unusual and concerning. (Unless it's extreme abuse or reoccurring... while surviving an attack like you describe is horrible, I would not consider it the sort of thing that would be remarkably scarring.) A child's near-death experience at the hands of a trusted adult wouldn't be remarkably scarring? I have to disagree, with respect. Once a child experiences something like this, chances are good that the child is no longer is no longer an average person. There is some pretty convincing research that shows trauma suffered in childhood affects the way a person's brain develops physically and chemically. Healing isn't a matter of time and counseling. Sometimes it simply isn't possible.
So her issue isn't trusting other people (or just male other people?), it's with trusting God and the universe? The death of a fiancé would certainly be psychologically painful, but not in any way dangerous. Your opening post said:
Yes, that seems to be the premise ... but that's not what immediately comes to mind when I read, "... I will always be in danger." Especially not when that statement follows close after, "My neighbor strangled me when I was seven years old."