Mona Vanderwaal lives in a normal house, in a normal teenage girl room, decorated with too many dolls to count. She had a very normal mother, who baked cookies in case that one friend her daughter made would ever come around - Hanna Marin's favourite cookies, she remembered. And Mona Vanderwaal could play this game better than almost everyone else save maybe one person, be two different people, change from one moment to the next, the daughter to her mother and the weaponized, perfected reaction to what Rosewood does to teenage girls: someone equipped with the ability to strike back, to take control of her life, to observe those who always miss the important things and gather the information that would give her power over others, over herself. Save one person.
There are many parallels between Pretty Little Liars and Twin Peaks: Both shows follow their own rules, which make sense in the context of the show but wouldn't, anywhere else. Birds providing vital clues for murder investigations, the importance and significance of dreams, dead girls haunting in memories and videos, doppelgangers showing up, then the girls themselves - but one of the greatest parallel is the idea that teenagers, and specifically teenage girls, always need to have more than one face to survive. Both shows map what happens because of that necessity. Alison DiLaurentis, whatever else she might be (and whatever else she might need to be, now that the show doesn't have a definite end, now that the show doesn't seem to be mapped out definitively), is the perfect example of someone evolving to be adjusted to her environment. Rosewood is filled with people (with men) hunting teenage girls, at best just trying to shape them into what they want them to be, at worst, taking control of them entirely. Alison recruited a safety net for herself, and she did it with what she had in her possession, being able to look at the girls surrounding her, seeing their weaknesses and using them, but at the same time, and as much as it helped her, giving the girls the tools to battle their weaknesses (but also making sure that bits and pieces would remain, so she could continue to control them). Mona Vanderwaal watched from the sidelines, tortured by the names Alison gave her, by the role she forced her to play, and she learned, she studied, and she became Alison's best student, up to the point where she tried to take control herself, and succeeded to an extent. Mona Vanderwaal made herself, with Alison's help, and she made Alison (that new, strange version of Alison, that disappeared and reappeared, with whatever happened inbetween), and then she made Hanna Marin too, who was eager to be shaped, and later, desperate to recover what she had buried so deeply, trying to find herself again (which is amazing because what has become of Hanna is so amazing, someone growing into all those empty spaces, learning all those skills she never had naturally, just excelling at everything, all the time).
Rosewood is what shapes them, a town where cops, meant to protect them, are at best incompetent but most of the time, part of the problem; where fathers know exactly what their daughters ought to be, exactly the opposite of the women (and college girls, and high school girls) they are cheating with. Another parallel to Twin Peaks: a more important question than "who killed Laura Palmer", which those who made the show never wanted to answer anyway, is, how could this happen? What kind of environment made Laura Palmer into the person that she was, someone who was thought to be something entirely different than she actually was, to the extent that the difference between the two so severely breaks many other characters on the show (Bobby, who, in a way, looked into that darkness and barely survived, James, always too simple to understand even a bit of it, clinging to what he thinks is easier until it grows beyond his grasp).
Both shows are about the power of secrets, the destructiveness of keeping them for yourself and keeping them for others, but also the potency of having a secret self in a town that is so restrictive in terms of what teenage girls can be. Alison DiLaurentis was a good girl, and Alison DiLaurentis was a terrible girl, terrible enough to almost have an army assembled against her. Laura Palmer was a good girl, until her secret life is revealed during the investigation of her death, but the way that she wasn't good was a reaction to the town itself, the horrors of secrets hidden in suburbia.
The difference between the shows is that Twin Peaks, while being able to explore the violence in much more drastic terms (because it isn't on ABC Family), offers an outside perspective, a naive but competent FBI agent entering and revealing. In Pretty Little Liars, there is no outside. Everyone who matters, everyone whose perspective matters, has been there since their childhood. There is no real outside, 'out of town' is at best mysterious and temporary (or doomed to failure). Terror does start at home, even if the show can never truly explore the horrors of it (Ezra Fitz was always going to be redeemed for his wrongdoings, there will always be a limit to how truly the worst Byron Montgomery could be). But maybe that limitation makes the show even more horrible than Twin Peaks: Audrey Horne's discovery of how truly awful her father is knows no limits, she realizes so quickly that she is expected to be a certain way because she is his daughter, while he has entirely different expectations into girls her age, going to the same school, but less economically and socially protected. All the terrible things that ever happened to Laura Palmer pale in comparison to the years of abuse she suffered at the hands of the person she was meant to be able to trust the most. And yet, the true horror of PLL lies in the fact that characters like Ezra Fitz can seemingly be redeemed, even after abusing every trust put in them, every expectations you might have in adults who are responsible for children disappointed and worse - the fact that Byron can come back into the Montgomery household and dispel fatherly advice, after everything that happened.
One of the most horrible moments, in a show that has literal jewellery made out of bones, characters trapped in boxes with dead bodies, loved ones buried alive and dead in suburban backyards, happened a couple of episodes ago, because Mona Vanderwaal met someone more prepared than she was: Hanna Marin was confronted with an impossible situation, realizing that one of her best friend's mum's future husbands was a horrible person, another grown-up abusing his position of power, and nobody believed her. Her skirt was too short, she was too drunk, she got into his car. She was asking for it. And these accusations didn't come from strangers: in a show built and circling around the faithfulness and compassion the four main characters have for each other, the unfaltering support they provide for each other, that promise of true, unconditional friendship, was utterly broken. It was a shocking moment for the show, because barely anything ever grazed that friendship, in the face of all the shockwaves and drama - and yet, a very eloquent choice, because this is how deeply misogyny is rooted, that a teenage girl would be blamed for the transgressions of an adult man, even by her own friends. The show recognized how utterly horrific victim blaming is, that it cuts to the strongest bonds even. The bonds were restored later, with much regret and apologies, but the wounds remain.
The thing about Mona Vanderwaal is that she shaped herself into a weapon out of love for her best friend, and she somehow acquired superpowers because of how much she loved her best friend, Hanna Marin, because of how much losing that best friend to others hurt. If her death should be permanent - which, considering how well-developed and loved and acted her character is, I will not believe until the show is over - it will be truly a tragic loss, in part because we know her motives, while Alison's still remain hidden. In a way, Alison loves power because the very system she operates in denies her power just based on who she is, a teenage girl. Her desire to regain that power at any cost comes from wanting to defy that system, or at least wanting to live within it with as much grace as she can muster, whatever the cost (and the cost is always other people's integrity - it's not even like she is using them out of spite, it's a natural instinct, as true to her nature as anything else). Mona Vanderwaal just wanted her only friend back, the one her mum is still baking cookies for, because she knows how unbearable this world is when you have to face it alone.
Pretty Little Liars (2010-), starring Troian Bellisario, Shay Mitchell, Ashley Benson, Lucy Hale, Sasha Pieterse, Janel Parrish, Lindsey Shaw.
Twin Peaks (1990-1991), starring Sheryl Lee, Sherilyn Fenn, Lara Flynn Boyle, Mädchen Amick, Kyle MacLachlan, Michael Ontkean, Dana Ashbrook, Richard Beymer, Warren Frost, James Marshall, Peggy Lipton, Joan Chen, Michael Horse, Piper Laurie, Harry Goaz, Ray Wise.