Two words. "Stockholm syndrome." That says it all. The behavior of bonding was recognized in the bank employees in Stockholm who bonded with and were empathetic with their captors who took them hostage -- and that was only for a few hours! For JC, it was 18 years!
Even if it was not Stockholm syndrome, JC had solid reason not to leave until it was under the conditions favorable to not only her own escape, but that of her daughters. Remember, he was the father and since the girls lived on his property and he recognized them as his own, under the law, he had parental rights to custody! How much JC understood this is unknown. However, even little snippets of this information would have scared her beyond reason. Her own mother and bio father had some history and he was not part of her life. Therefore, it is not unlikely that she had some inkling of these issues even if incorrectly.
Sadistic perverts like this also commonly have a history of abusing animals. So, where is the cat that goes with the kitty litter and pet food bowls. Where are the pitbulls the neighbor saw in 2006? Where are the 2 four year old girls (boys?) the neighbor saw in 2006? What are those blood smears from? Who was screaming when the 8 - 10 men were there frequently having bonfires and beer? Crazy Phil scared the neighbors. Is it not a small step to know that he terrified JC and her daughters? Terror also constitutes invisible chains. One daughter even had to ask permission to go across the room. Another had rehearsed her lines even to the point of describing her mother as her sister. Robotic? Lesser forms of catatonic conditions? Stress induced catatonic states? Were the animals killed in front of the children to terrify them as was alleged in the McMartin Pre-school cases? Terror tactics are proven invisible chains and gags. At the first opportunity of having her daughters and herself in the presence of a uniformed law enforcement officer, JC did identify herself. That is the only thing that counts. From the day Nancy grabbed her until that moment, the kidnapping and the effects thereof were continuous. Only ignorant people will further pursue this idea that she was not captive during any part of that time frame.