CHARLESTON, W.Va. -- When Janel Parrish auditioned for ABC Family's "Pretty Little Liars," she knew the soapy teen thriller was going to be popular, but she didn't know how popular.

"I read the script and saw the hype behind the books and said to myself, 'This is going to be huge,'" the 23-year-old actress, who comes to Charleston Town Center Mall on Aug. 18 for a fan meet-and-greet, said.

Parrish, who is also a singer-songwriter, initially auditioned for the role of Spencer, one of the four main girls. She said because of the quality of the script and her gut feeling of the show's success, she was disappointed when she thought she wasn't going to be part of it. That changed, though, a few months later, when she was called back to audition for the supporting role of Mona, which she got.

When Parrish first began the audition process, she hadn't read Sara Shepard's book series that the show is based on. She began reading to familiarize herself with the story.

"I read the books to get familiar and ended up falling in love with them," said the Hawaiian native, adding that the first one, "Pretty Little Liars," is her favorite. (There are currently 12, with another due in December.)

"I really liked it. It's a good introduction to the story, and it sets up the characters really well."

Those characters include the core group of Spencer (Troian Bellisario), Aria (Lucy Hale), Emily (Shay Mitchell) and Hanna (Ashley Benson), four young women who were once best friends but drifted apart after their clique's leader, Alison, disappeared.

A year later, which is when the show begins, they're reunited in a most unexpected way -- they start getting text messages from "A," who threatens to expose their darkest secrets. At first, they think it's Alison ... but then her body is found. And the text messages continue.

Parrish's Mona is Hanna's friend. The actress said that when Mona was younger, she was bullied by the clique. Mona and Hanna transformed themselves, though, into the most popular girls at school.

"I can relate to certain aspects [of Mona], like the vulnerability she used to have," Parrish said. "I think every girl in high school at some point can relate to trying to fit in and pleasing their peers."

There's one big aspect of Mona that Parrish can't relate to: her madness.

"Mona is 10 different people all rolled into one psychotic person," she said with a laugh.

That psychosis came to a head in the season two finale, when Mona was revealed to be "A" -- or at least one of them. Though Mona is placed in a mental institution, the girls still hear from "A."

"Mona has infinite personalities," Parrish said. "She's cold, calculating, manipulating and definitely a little insane. She's really dangerous. You never know what she's going to do."

Parrish found out her character would be "A" about a week before the finale was shot. It was exciting but not entirely unexpected. She said she'd had some hints from producers and also knew that Mona is "A" in the books.

"I was reading the books when I got the part. I'd just gotten to the part in the book where Mona was 'A' when we were shooting the pilot. I was excited that I could be this character, but I didn't know for sure it would be me until two years later."

Fans' reactions to the reveal were mostly great, Parrish said, though she noted, "Some were disappointed because they liked Mona's character. I had fans tell me, 'I can't like you anymore.'"

"But a lot of people like crazy Mona," she added. "Crazy Mona's fun!"

Just because Mona is in a mental hospital doesn't mean she's out of the picture, though. Among her activities this season, she clued the group in on a website belonging to Maya, who was Emily's girlfriend.

Maya was found dead in the season two finale, and Parrish said that by the time the show goes to midseason break Aug. 28, "the site will ultimately lead them to who killed Maya."

As for the future, she noted, "There's a special Halloween episode [in October], which we had last year as well. There are some very exciting events you don't want to miss if you're a 'Pretty Little Liars' fan."