IMO she is an evil Sociopath. A Sociopath who kills. I'm sticking with what my gut tells me. Unless something comes forth to convince me otherwise.
Female Psychopaths/Sociopaths are pretty rare. They are like the 1% of the 1% of the US population that may have an Anti Social Personality Disorder. A woman who most likely was a sociopath was Sante Kimes, who murdered a couple people with her son, Kenny Kimes.
I don't know Magen Fieramusca behavioral issues, I think she may have some mental health issues like depression or anxiety, given some of her traffic tickets were most likely from negligence, (some of them were pretty serious) plus her mannerisms in Traffic Court.
One has to have an Anti Personality Disorder to be a serial killer, but those with an Anti Social Personality Disorder doesn't mean they will kill, but they can have no empathy of others, (felines are sociopaths by nature, which doesn't mean your cat is a monster, they just can feel much empathy), for doing what they enjoy, like petty crimes. There is still not enough out there to get a firm judgment on Magen's Behavior. I don't even know if she strangled her best friend, Heidi, or she got someone else to murder Heidi.
Sociopaths also have a difficult time maintaining friendships and relationships, given they can't show empathy for others, which makes it difficult for long term relationships. They have no qualms in getting what they want if someone is standing in the way. However, there has to be a long pattern by Magen showing this behavior. More information will come out about Magen. Her friendships, her relationships, her mannerisms will be made public to get a better picture of her behavior throughout the years and why she is accused of this heinous crime of kidnapping and possibly murdering her best friend.