Video of the ex-girlfriend of Aaron being questioned by LE appears in American Nightmare, so yes, she's real. She was actually another co-worker at the couple's place of employment. One of the agents working on Denise's case was an ex-boyfriend of the ex-girlfriend.
It's possible Muller was stalking the couple and recorded or overheard their discussion about his ex-girlfriend. In the podcast linked above, Aaron believed that someone had broken into his house not too long before the abduction. Things had been moved around or were missing, etc.
According to the first epi of the above podcast, Aaron's brother is actually an FBI agent. He was the one who told him to call LE instead of trying to cooperate with the kidnappers. After, LE lied to Aaron's brother about what Aaron was saying, making it sound like he was guilty. They also lied to Aaron about testing his blood to see what kind of drugs the kidnappers gave him to knock him out.
The manipulation and coercive control/psychological techniques used on both Denise and Aaron were very similar. It made me wonder if Muller was an LE wannabe and hung around with the local LE. He lived with his mother on Mare Island. What if Muller talked others into doing the kidnapping as a sort of game or project to test their skills? What if some of the people who helped him plan it were actually LE? Did Muller or Aaron's ex-gf hang out in any local "cop bars"?
JMO only
Also, the S. Lake Tahoe woman detective mentioned that her search of the info on Muller's white Mustang revealed it was stolen from Vallejo. Why didn't Vallejo LE make the connection between the kidnappers white Mustang and the one that had been stolen?
So many questions.