BBM- Shady, that is a very difficult thing to determine with any amount of confidence given the limited information and all the lies that have been told but I will give it a try.
From the limited information out there, in conjuction with the writings and behavioral observations of Travis' murderer, she is in fact a BPD. However, what was not allowed in but was indicated on MMPI subscales (as well as her observable behaviors/actions and the collateral reporting of others) is that she also had Narcisssistic traits. To say someone has "traits" of PD is very significant in the field, and honestly I'm not sure why a "Rule Out" of NPD wasn't included in her diagnostic evaluation. To diagnositically denote/document a Rule Out is the Clinician's way of saying that they see indications and are fairly convinced that this condition does exist, however the criteria was not fully met at the time of the evaluation.
In any event, it appears, based on what has been revealed, she has psychopathy, and a central feature of this condition is a complete disregard or concern for rights or feelings of others, as well as a profound lack of empathy in the pursuit of fulfilling their needs/wants/desires. They make their own rules. They feel entitled and important. Basically getting what they want at any cost. So the need for control in those with psychopathy is a means to an end.
In normal adult individuals who have a need to control, it is usually (but not always) a result of having little to no control in threatening or unhealthy environment--and the underlying issues of said environment go unresolved/not addressed. The one thing that could be considered as a possibility regarding Travis' murderer, is that given her promiscuity and use of sex as a means for control and manipulation, could indicate sexual abuse in childhood. Now, understand that I am in no way saying this is true, what I am saying is that any Clinician worth their salt would work to determine if there was.
And finally, as the to "nature vs. nurture" issue, it is my stance that nature and nurture enjoy an interdependent relationship in which each influences the other, but to what degree is debatable. For example, there have been numerous cases where a sibling group of 5 were exposed to substance abusing, violent parents and 3 of the children are emotionally damaged and highly dysfunctional, yet 2 of them grow up to be happy, successful, and well functioning adults.