Married at First Sight expert Dr. Pepper Schwartz admits she's worried the bright light inside Kate Sisk is going to burn out in her unhealthy marriage to Luke Cuccurullo on the show.

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"What really bothers me and what I really have to see a change in, is that the Kate I met when going through the interview process was a bubbly, happy, open person," Dr. Pepper said during Tuesday night's Married at First Sight: Unfiltered episode hosted by Jamie Otis.

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"And Kate has become sort of -- over these days -- less of the Kate I met."

Ever since Kate said, "I do," to Luke on Married at First Sight's eighth season, it's been an uphill battle.

Luke told Kate during their honeymoon he's not physically attracted to her, and then at one point, Luke told producers behind his wife's back that he thought she had a drinking problem.

Kate has found herself in one dark place after the next, all the while trying to make Luke happy and their marriage work.

"To me, a marriage should make you happy!" Dr. Pepper told Kate on Unfiltered. "It should bring out the best in you and make you feel better about yourself! And that hasn't been happening, so I find that very discouraging."

Kate confessed on Unfiltered the process was like "a roller coaster" for her.

"I'll have a breakthrough and then I'll talk to my friends and they'll bring me back down to reality, like, 'Hey, I know you feel you had a breakthrough, but you only went from the bottom to maybe the first step and you have so much longer to go,'" Kate explained.

Kate and Dr. Pepper were also joined by Season 8 Married at First Sight star Kristine Killingsworth, who appears to be happily married to Keith Dewar on the Lifetime reality series.

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"It's just been a few weeks and you already have so much drama -- he's not attracted to you, he thinks you're drinking too much," Kristine told Kate. "When is everything actually going to start working out?"
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"You say he's a nice guy," Kristine added, "but we haven't actually gotten to see it."

Kate acknowledged Kristine's assessment of the situation was "fair," and then Jamie asked Kate how that made her feel.

"You're right, [Kristine], but... Luke is very charming and you can't forget that. Like, what looks like he's a nice guy, maybe that's just his charm," Kate reasoned.

"But also, this is a marriage, I made a commitment, and he says he wants to try. So I can't just give up because it's my husband! So, I have to just keep going."

Dr. Pepper pointed out Kate's dedication to her marriage is exactly what the Married at First Sight experts hope for and expect from their participants every season.

"I hope Luke can open up and be more clear and honest and I can understand him," Kate told Jamie.

"He says he wants this to work and I have to have some form of trust that if he says he wants to continue and work on this marriage, then I want to do that too."

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Married at First Sight currently airs on Tuesday nights and also stars AJ Vollmoeller and Stephanie Sersen as well as Jasmine McGriff and Will Guess.

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