But her sister and brother-in-law, Louise and David Turpin, kept such a secret life that they wouldn't let her in.
"When that happens for 20 years, and it was before the kids even were there, you don't think it's abnormal," Flores told ABC's "Good Morning America" on Wednesday.
"If it had been like two years ago that she cut us off, then we might think, wow, something's not right. But this has been going on before they even had children ... they were real private, and they didn't come around much."
The world now knows some of what was happening inside the Turpins' 4-bedroom house. Their 13 children were held captive -- with some shackled and chained with padlocks.
Now the children are free, and the parents are in custody. The Turpins face charges of torture and child endangerment; bail was set at $9 million. It was not immediately clear whether they have hired an attorney.
Sister-in-law: He watched me when I showered
Flores said she was never really comfortable with her brother-in-law.
Back when she was in college, Flores lived with the Turpins for a few months. At that time, the couple had a few children.
"I thought they were really strict, but I didn't see any abuse," Flores told GMA.
But something very disturbing did happen: Turpin used to watch Flores shower, she said.
"If I went to get in the shower, he would come in while I was in there and watch me. It was like a joke," Flores said. "He never touched me or anything."
But she said she never told anyone about the shower stalking.
"I was young. I was scared. I was in Texas, where I knew nobody," Flores said. "I was treated like one of the kids, kind of, so I had rules. Well now that I'm an adult, and I look back, I see things that I didn't see then."
As the family grew, Flores said, Louise Turpin even shut out her own father.
Several years ago, she said, her father booked a flight to go see Louise and her family.
"He got the ticket, he was going to surprise her, and he called her to tell him he was coming. And she told him not to come."
Another sister: The kids looked really skinny
Teresa Robinette, another sister of Louise Turpin, said she sometimes kept in touch with the mother of 13. But she was concerned about the children's weights, Robinette told NBC's "Today" show.
"I always made comments to Louise when I did talk to her, about, 'Gosh, they're so skinny.' And she would laugh it off: 'Well David's so tall and lanky. They're going to be like him,'" Robinette said.
After hearing about the children's alleged torture at home, Robinette broke down in tears.
"We are as hurt and shocked and angry and disappointed as everybody else," she said.
Flores said she, too, was devastated to hear what happened. But she said she still loves her sister.
"I want her to know that she's still my blood, and I love her," Flores said. "I don't agree with what she did, and her actions has made the whole family suffer. But I want her to know I'm praying for her salvation."
Flores said she had a more important message for her nieces and nephews:
"I want them to know they do have family that they love, whether they know us or not."
Aunt: Everybody wondered why they had 'all them kids'
Brenda Taylor, who is Louise Turpin's aunt, said she wasn't around her niece often, but followed the couple's lives on Facebook.
"With the pictures they put on Facebook, you thought they were one big happy family," she said.
David and Louise Turpin were both from Princeton, West Virginia, she added.
"She was young when they married," Taylor said. "She was 16, I think."
Taylor said she hadn't seen them in West Virginia since the mid-1990s when the couple had only two children. She said that they didn't come home for Louise's parents funerals and that she wasn't in direct contact with the family.
"Everybody in the family was always wondering why they had all them kids," Taylor said. "I never dreamed they had all them kids."
But she would comment on their Facebook page, but never got a response back.
Taylor said she was shocked to hear of their arrest.
"We always thought she [Louise Turpin] was the most stable of them," her aunt said. "Now it sounds like she was the worst of them."
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