Tonight, ABC Family’s Pretty Little Liars had its season finale. The cable channel cashed in on the phenomenon of today’s mothers and daughters watching the same TV shows with The Secret Life Of The American Teenager, so Marlene King was to target the same mother-daughter audience when she was asked to develop Pretty Little Liars. Based on young adult thrillers by Sara Shepard, the series is a product of Gossip Girl‘s Alloy Entertainment. In this interview at Warner Bros, King, who co-runs Pretty Little Liars with exec producer Oliver Goldstick,  talked to Deadline contributor Diane Haithman for this Showrunner Q&A about how a 47-year-old mother of two young boys came to partner with Alloy, Warner Bros, and ABC Family on the story of four small-town girls with secrets who start receiving mysterious text messages from their “missing” best friend:

DEADLINE: How did you get involved in this show?
KING: In a traditional world, I would have met with Alloy, then met with Warner Bros, then met with ABC Family. But we did it in reverse, and we did all right. I had a general meeting with ABC Family. I had only written features [Now And Then, If These Walls Could Talk, Just My Luck] and dabbled in TV only one other time. I had written a pilot for what was The WB. Kate Juergens was over there as WB’s SVP of development and she is now EVP of original series programming at ABC Family. And we had such similar sensibilities, we were like long lost friends. I knew we could do something together. And the next day they sent me the first Pretty Little Liars book.

DEADLINE: Had it been in development long?
KING: Before I came to the project, it was in development at The WB, and again at The CW. I think they tried to develop it twice at The CW. And then Alloy at WB took it to ABC Family. I think it was a perfect fit for me. I come from the heartland and I grew up in a tiny tiny town, and so I know that world very well. It was relatively easy getting the pilot made and getting the show on the air and staying true to what it was. The only struggle we had originally was the tone. We probably had 50 ‘tone’ meetings before we made the pilot. But it is what makes Pretty Little Liars unique unto itself. It is a little bit of mystery, it is a little bit of soap, it is a little bit of heightened reality, it is so many things rolled into one that it became original in that way.

DEADLINE: How did it affect you to have Paul Lee leave as head of ABC Family and become president of ABC Entertainment Group?
KING: It hasn’t really. We were nervous that it would because Paul was a huge champion of this show, and he embraced the darkness and the edginess very early on,. It is a very different show for ABC Family. But the executives over there have been very true to what the show was early on. They have told us many times, ‘If it ain’t broke, don’t fix it.’ Paul is still very very proud of this show and checks in often to see if we’re all happy. I think he thinks of this as his baby, too. Kate Juergens continues to spearhead what this show is, and she has stayed very true and solid with us about the process.

DEADLINE: Speaking of dark and edgy, you have situations on Pretty Little Liars where a mother sleeps with the cop who arrested her daughter for shoplifting.
KING: On our show it’s about secrets and lies. But what we loved the relationship that Laura Leighton’s character, Ashley Marin, has with her daughter Hanna [played by Ashley Benson]. They have their own moral code. They are teammates. They know they can count on each other. They’re certainly not a traditional family, but then, we don’t live in a traditional family world.

DEADLINE: I just watched an episode where a girl is blinded because of a prank the girls played.
KING: That’s where, as writers and as creators, we really enjoy the show. Because the girls are complex. At Warner Bros, when we sat down and started pitching out the season to Peter Roth, he had a very legitimate concern that these characters were going to be hard to like. They have made mistakes, and they do lie over and over again. But because we gave them backstories that were relatable, you understand why they made their bad decisions. We found that people are liking them. We’re all liars.

DEADLINE: In terms of the standards of ABC Family, where do they draw the line?
KING: They definitely do. They draw the line at bad behavior without consequences. That is their line. If someone shows bad behavior, it can’t go unpunished or unnoticed. A storyline we were really proud of from last season was Emily’s ‘coming out’. It seemed to be embraced in large part by our audience in a very positive way. Now Emily is just Emily who happens to date girls. Our characters are really true to the books, and that was Emily’s character. But next season we want to tackle the issue of teen depression. We are trying to, every year, find something that matters.

DEADLINE: Could this TV show segue into a feature film you would write?
KING: I know that Alloy would love to create a feature franchise with this. We’ve talked about doing a feature film once the girls get older. But I think it’s definitely the golden age of television for women in the sense that ensemble movies aren’t getting made, but ensemble TV shows are on ABC Family and Lifetime. There was a time when possibly networks weren’t embracing the fact that it is women who are watching television. My niece goes to college at Syracuse, and Monday nights are Pretty Little Liars night. Every dorm room has it on. But teen girls don’t necessarily watch TV live. It’s all iTunes and Hulu. But this show, because it’s a mystery, is becoming destination TV.

DEADLINE: Because this show has a massive marketing component, do you ever feel it overwhelms the writing?
KING: No, because we still sit in a room and say: ‘Here’s what’s going to happen.’ We still come up with stories the way we did 5 years ago, and 10 years ago, and 15 years ago. The marketing has made the show more accessible to people, but it hasn’t really changed the way we create the show. The whole social networking aspect of this show has been phenomenal. It’s not just a great business tool for us. We get instant feedback on what storylines are working. It would be devastating if you were invested in some big storyline and your audience just couldn’t relate to it. For us it has been mostly validation that we’re getting it right. But if you get something wrong, they’ll tell you. Though we have done some shameless TV tie-ins. I think an older audience might say, ‘Hey, why is everybody driving a Toyota?’ But for this younger audience, they’re used to it. I was talking to someone recently about how we are very close to the technology where you will be watching the show on your computer and you will click on Aria’s blouse and it will tell you immediately: ‘Available at Macy’s for $29.95’.

DEADLINE: What other TV shows do you watch?
KING: I watch Gossip Girl, Vampire Diaries, True Blood. I think I somehow got stuck in my teen adolescence. Maybe I’m still playing out those stories.