'Vanderpump Rules' Stars Scheana Shay and Katie Maloney Tease Season 4 Secrets, Reveal They Have PTSD: Post-Tr

Less Stassi somehow means more drama at SUR!

Four years ago, Scheana Shay and Katie Maloney couldn’t stand each other. Now they’re best friends -- and that friendship is at the heart of Vanderpump Rules’ fourth season.

“We've all grown,” Scheana told ETonline about what’s different this season. “I feel like Katie's changed so much, but in the most positive way ever and grown into someone that I cannot not see myself being friends with for the rest of my life. Like, she's my go-to girl.”

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According to Katie and Scheana, getting Stassi Schroeder out of the picture really helped bring the two women closer together.

“I have a threshold for everything, so, I threw my hands up,” Katie said of ending her friendship with her former fellow SUR server. “And when I did that, I was free to do what I wanted, and have opinions about things, and not be judged or criticized for it.”

But just because the Pucker & Pout founder ended her friendship with Stassi doesn’t mean Stassi is out of Katie’s life. The 27-year-old returns this year in a recurring role, even though she very publicly announced she wouldn’t be back after a rough third season.

WATCH: Vanderpump Rules Star Stassi Schroeder Reveals the Truth About Her Sex Tape and Plastic Surgery

“When we all found out she was returning, we were all like, 'Why?'” Katie said. “Like, so confused and suspicious about the timing, because she had so publicly trashed all us and the show, the fact that she's now come crawling back, we're all like, ‘We're not gonna make this easy on you.’”

“And we did not,” Scheana confessed, though both stars teased that Stassi’s return had a surprising outcome -- they just couldn’t tell ETonline about it.

“Because then, you know, 20 weeks of the show are just gonna be gone!” Scheana said.

“It's better to watch it, because you can't articulate it,” Katie added.

The ladies did give some hints about their current feelings toward Stassi during a game they played with ETonline. Check out Scheana and Katie’s SUR yearbook superlatives for their Vanderpump Rules cast members:

Stassi will only appear in a handful of episode this season, but Scheana and Katie suggested another full-time cast member is stepping up to the plate with some Stassi-style drama this season.

Ariana Madix, Scheana’s longtime friend, starts to question their relationship in the season four premiere, because Scheana will not cut Kristen Doute out of her life. Kristen, of course, used to date Ariana’s boyfriend, Tom Sandoval -- and said she wanted Ariana to get hit by a train during season three.

Kristen shows up uninvited to Scheana’s 30th birthday party on the season premiere, and the makeup designer refuses to kick her out of the party -- even though that’s what Ariana seemingly wanted.

“Ariana's still one of my closest friends and I didn't feel right inviting Kristen,” Scheana said. “I had a feeling she was going to show up, because [her boyfriend] James invited her, and I'm like, 'Well, she's not gonna miss a party.'"

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At one point in the episode, Madix wonders if Scheana is a “fake friend.”

“Those are the things that, you know, normal people in normal lives don't get to see their friends say behind their back,” Scheana said. “But we film a television show and then six months later, I'm like, 'Oh, so that's how you really feel about me? Tell me more.'”

“I mean, just because Kristen went in and I didn't physically remove her from the building, it doesn't make our friendship any less,” Scheana continued. “It doesn't discredit anything, and I feel like Tom and Ariana are like, 'You're either with us or you're not!' and it's, like, I can be with both.”

“You see [Scheana] said, like, ‘I wish sometimes people would give me a reason not to like them,’” Katie added. “Like, give me a personal reason, and she's like, 'Well, I am a reason.' I mean, that felt very flashback to Stassi last year.”

WATCH: Vanderpump Rules Star Stassi Schroeder Says Her Relationship With Lisa Vanderpump Will 'Never Be the Same'

“Like I said, [Kristen] needs to give me a direct reason,” Scheana continued. “She needs to personally hurt me. Hurting you doesn't hurt me … If Kristen tried to sleep with my husband, that's a direct reason.”

“It's like so weird deja vu,” Katie confessed, admitting to having a touch of PTSD: Post-Traumatic Stassi Disorder!

“So bad!” Katie said. “I have a physical reaction [to seeing her]. My eyes twitch and ass my clenches.”

We’ll get to see that eye twitching and ass clenching play out later this season. Vanderpump Rules airs Mondays at 9 p.m. ET on Bravo.

To further gear up for Monday night’s premiere, check out our interview with Stassi about her return to the show below.