'Welcome to Plathville' 's Olivia Plath Reveals Her History with Kim — and Their First Argument

The friction between Olivia Plath and her mother-in-law, Kim Plath, started long before Welcome to Plathville.

In an exclusive clip from Tuesday's season 4 finale of the hit TLC series, Olivia, 24, shares the history of her relationship with Kim, which began when she was a teenager, well before she married Ethan — and approximately eight years before her "meltdown" at the memorial for Joshua Plath in April.

"I met Kim when I was 16 and she, when I first met her, made me feel important," Olivia recalls. "She kind of took me under her wing and in many ways kind of made me her new best friend. She was calling, emailing me every day."

Olivia continues, "I trusted her more than I did my own mom, and at that point in my life, I really, really needed a mom figure. Because the mom I had was not nurturing, and also being one of 10 kids, it was really easy to feel overlooked and forgotten and I just really needed to feel important to someone."

"And you loved her?" a producer asks Olivia of Kim, 49, who is also a mother of 10.

Olivia gets emotional as she nods her head yes.

"I think what changed is when I started to realize that I was just being used," Olivia says. "I felt like I was only of value to her if I did what she wanted me to do."

Olivia goes on to give an example of an early instance where she went against Kim's wishes.

"I will never forget marrying a 20-year-old man who his mom was using his credit card and buying things for herself and not paying him back," she says of the early days of her marriage to Kim's son Ethan, now 24.

When she asked him why, she says Ethan responded, "Well, I don't know the computer password, and I don't know the password to my account, so I can't stop her."

"Those were literal what-the-f--- moments," Olivia continues. "And so many of those happened. And I remember I changed his password for him and she's like, 'Oh, can you send it to me?' And I was like, 'No. That's his password now.' And that was the first time she ever blew up and yelled at me and slammed the door on me when she had me come meet her in town over that."

The experience changed Olivia and Kim's relationship permanently.

"It went from like, 'I love you so much' to 'You have the devil in you,' and it just kind of changed overnight," she says. "Being wanted by someone doesn't mean they love you. They can want you because you meet their needs, not because they want to meet yours."

The clip cuts to Olivia's brother, Nathan Meggs, 19, addressing Ethan and Micah Plath, 21, on his sister's behalf.

"You guys might be where you're OK with your mom, you're OK with anybody, you might be able to move on from what you call a grudge, but everybody takes different time periods to work through everything," he says.

But Ethan is clearly still upset over what happened in Cairo when Olivia opted not to attend a memorial for his dead brother because Kim would be there.

"If drama and just complicated nonsense or whatever keeps coming, whether it's from my mom, whether it's from you, like I do not know how I'm going to handle it," Ethan says. "I'm really kind of at the end of my rope as far as dealing with all that."

RELATED VIDEO: Welcome to Plathville's Moriah Plath Has Reached a 'Breaking Point' with Olivia: 'I'm Done'

In last week's episode, Olivia's best friend and sister-in-law, Moriah Plath, 19, shared a similar sentiment.

"Today I have officially reached my breaking point with all of this drama," Moriah said. "I am so done. I am so over it. I'm just tired of fragile relationships. If you have to constantly walk on eggshells around somebody's feelings, if you spend three to four years of your life trying to make that person happy and then you make one decision that doesn't make 'em happy and it affects your whole relationship? That's not a true friend. And it hurts to say that, but that's the harsh reality I'm waking up to."

Moriah added, "I love Olivia, but if somebody's going to make me choose, I'm going to choose the person who's not making me choose. I'm done choosing."

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The two-hour season 4 finale of Welcome to Plathville airs Tuesday at 9 p.m. ET on TLC.