Totally agree with all of this ^^^
Nancy was likely killed the first night, dumped( very sorry) in the desert outside of town.
Why is the question, who would want her gone.
I speculated earlier in thread, NG saw something, maybe as simple as drugs in a workers trunk (his moonlighting job), he was at her house working on a job, maybe the roof. Maybe she even said “ is that drugs?”, he waved it off, “no worries, just materials for a job”, closed trunk.
Later, The person decided it was too big a threat to have her live, she might turn him in.
Just another idea to think about, JMO.