Being with a sociopath is a lot like staring into the eyes of a tiger. It’s so dangerous and fascinating that it draws you in. You’re dealing with someone with no love, no morals, or a conscience, and it doesn’t matter how long you’ve known her. It isn’t easy to figure out what she wants, but once you get in her way, she won’t hesitate to tear you apart. I know this because I grew up with one. Her name is Ellen (not her real name), and she happens to be my sister. Ellen was always a petty crook. By the time she was seven years old, she was swiping cash from Dad’s wallet and taking candy from the deli. She was 10 when she started shoplifting. I remember going with my parents to pick her up at the police station. The owner of the local boutique was there, bristling and defensive. He said the last thing he wanted to do that day was drag a little kid all the way to the station. One little apology and he would have let her go. Instead, she had denied everything — even after he shoved the items under her face, and told her he had it all on camera. RELATED: It Took Me 26 Years To Fall In Love My parents had nodded sadly. Ellen had done this many times before. She would persist in lying even when all the evidence was against her. It was infuriating. From my sister’s point of view, it was like poking a stick at a chained dog, just to watch it lash itself into a frenzy. I think she enjoyed it. From an early age, Ellen knew the value of secrets and lies. She used them for blackmail and to manipulate people. She tried to keep her family in the dark, but she couldn’t always resist boasting about the things she’d done. I wouldn’t otherwise have found out she had been toying with one of her elementary school teachers. She had accused him of sexual misconduct with one of her classmates. “I told him he shouldn’t have touched her,” she said, and she was proud of herself. “I think I scared him. From now on, he’s officially my bitch.” She was right. There was no scandal at school that year, and Ellen got all As on her report card. In her world, I suppose that’s a fair exchange. Then there was the time she told me she had memorized our grandparents’ Social Security Numbers and put them to use. I was horrified. I said, “Grandma has dementia, she’s 95 years old and she could die any minute. Don’t you care?” “It’s not like she needs it. Why shouldn’t she help me get a new cell phone?” Her stories left me stunned and breathless because they were things that I could never do. In spite of myself, I admired her for her audacity, her incredible drive, and persistence. I have wasted a lot of time over the years, searching for qualities in her that just weren’t there. I tried to love my sister, the same way I would have loved a handicapped child or one with Down’s Syndrome. But instead of missing a limb or a chromosome, Ellen lacked warm and fuzzy feelings as well as a conscience. All of my efforts to get close to her had no effect. To Ellen, I was a potential victim, just like everybody else. This became clear a couple of years ago when she asked me for a loan. Ellen was moving, and she needed a few thousand dollars to put down as the security deposit on a new apartment. I said yes. Six months and no payments later, I got a phone call from my sister. At first, all I heard was some really loud sobbing. It struck a false note because I had never heard her cry like that before. I instantly knew — before she even said a word — that she was going to lie to me. RELATED: The Factor That Can Predict Exactly How Long You’ll Live Ellen said, “I’m having such a hard time paying for school, rent, and everything else. Now, Mom is driving me nuts telling me to pay you back… but I have so many bills to pay. I don’t know what to do!” It was a long, self-pitying monologue, but eventually, I pieced the story together. Over the past few months, Mom had grown increasingly anxious about my loan, so she had stepped in and wired the funds to my sister so that she could pay me back immediately. Ellen had been thoroughly irritated by Mom’s nagging and wanted it to stop. But once she saw all of that beautiful money sitting in her account, she had no intention of letting it go. That’s when she decided to call me up and ambush me with tears. It was a distraction, meant to convince me to let her do what she wanted, which was to keep the money and keep it secret so that Mom would stop her yapping. I was appalled. She could have apologized, and she could have asked for my permission. Both of these would have been far better options than crying fake tears into the phone. I would, a million times, rather give Ellen the money than have her take it this way. It had been clear to me for a while that Ellen was greedy. That wasn’t the whole truth, though. She also loved toying with people. My sister wasn’t doing this just for the money. She wanted the thrill of stealing something, and of tricking people into giving it to her so that she could laugh at their gullibility and feel really smart. She was playing a game, we were the pawns and she found it exhilarating. She revealed this side of her character the last time I made an effort to please her. She had been behaving nicely for a while, so I decided to take her to the mall, buy her a few things, and give her a perfect day. It didn’t turn out the way I had expected. Ellen was quick to steer me into the Louis Vuitton store, where she started pointing out things I couldn’t afford. I had to shake my head no. It didn’t take long before the warm feelings of generosity I had burst into pieces. Her next move was to hold up a white dress with pleated ruffles. She said, “Will you buy me this? I could wear it to your wedding.” RELATED: 1 In 100 People Are Psychopaths — The 3 Personality Traits That Give Them Away I had my doubts about the color, but she was being sweet, for once. I was caught off-guard when I looked at the tag though, and it wasn’t the price that made my head explode. “This is six sizes too big,” I said softly, so I wouldn’t shriek. “You don’t even want it.” “It’s a joke,” said Ellen, and she burst into giggles. Then things got much, much worse. “Never mind,” said Ellen. “Let’s skip the high-end stores. All of the ladies are staring at you because you’re so much fatter than they are. Besides, you’re so big that they won’t have anything to fit you.” I watched her walk away from me and I started to wonder how my size 4 hands would feel wrapped around her scraggy, size 0 neck. Ellen had chosen to make my love foolish, my generosity a joke, and rip my self-esteem to shreds. She did it all without any provocation. She did it for fun. This is what Ellen sees when she looks at me. Since that day, I haven’t been able to let her back into my heart. Loving her had always felt like I was throwing all of my affections down a deep, yawning hole of need. Ellen always wanted more, more and more, but it was only because love made me a better victim. There was never going to be any sort of return since she just wasn’t capable of it. I started to wonder if I had some sort of moral responsibility to warn people about her. I faced this dilemma when Ellen introduced me to her boyfriend Simon (not his real name). He had dinner with my sister and me, and I liked him immediately. He was personable, and he talked easily about his job designing motorcycles and how he’d met Ellen while working in the same office building. RELATED: After I Became Emotionally Healthy, I Let Go Of My Best Friend Of 25 Years He told me that he wanted to marry Ellen, but he was worried about getting our parents’ approval. He had 10 years on my sister, and they might think she was too young and vulnerable to get involved with him. I could have laughed in his face. Ellen wasn’t vulnerable at all. She was the type of person who liked to break hearts and eat them for breakfast. If Simon was truly in love with my sister, he wasn’t just in trouble, he was roadkill. I wanted to ask, Do you know what she’s capable of? She lies all the time, and even though I’m her sister, I don’t know what she does for a living or even her address. My head started to pound, and I was pretty sure that victims of sociopaths everywhere were egging me on to expose my sister and save the next few years of Simon’s life. I couldn’t do it. I don’t think I considered it for longer than a second, really, and I’m pretty sure it happened because Ellen and I are fundamentally different. I was afraid that she might really like this guy, and it wasn’t in me to risk-taking that away from her. Even though she enjoys hurting me, the last thing I want to do is hurt her back. xoJane was an American online magazine from 2011-2016 geared toward women and founded by Jane Pratt and co-published by Say Media. This article was originally published at xoJane. Reprinted with permission from the author.