Transcript for Woman says she was swindled out of $200K by man she met on Tinder

Reporter: He was handsome. Charismatic. And seemingly wealthy beyond measure. For Celia feloy, it was an easy decision to swipe right. This guy Simon comes up on my phone. You can see that he lives a very different life than what I'm living. He had some selfies, a picture in a nice car. You could see that it was a private jet. It is an overall package. Reporter: The 29-year-old grad student studying in London says she was immediately swept off her feet by Simon and swept into a high-powered world of luxury. Just his aura and charisma. Reporter: After all, most of our dates don't end with a trip on a private jet. They take you to get on this plane and you go to Bulgaria? Yeah, I was texting my friends at the same time, like I don't know what's going on. You stayed with him. You had a nice time. Yeah. Then you came back to the uk, then what did you think? This was going to continue as a relationship? When I started feeling, okay, this guy is actually really nice and funny, and he is someone that I could date, and like maybe have something with. Reporter: A dream of finding Mr. Right went horribly wrong. I hate him. It's so horrible. Reporter: Celia says Simon told her he was an Israeli millionaire with a nickname the prince of diamonds. But he wasn't who he said he was. I'm sorry I'm crying over this. But it just comes, I can't help it's just so painful. Because I hate myself. I just hate that I did this, you know? Reporter: According to Celia, their brief romance turned into a real-life nightmare. Celia alleges Simon defrauded her out of $200,000, leaving her spiraling into debt, suicidal, and fearing for her safety. He manages to do this because he is a great guy who pretends that he cares so much for other people, so you want to care for him as well. A lot of people watching might think, if it was 3,000 or 4,000 pounds I would start to feel like I need this money back. You let it get to 200,000? I know it sounds so crazy for people, but the sums weren't a lot. And I could see the spend that he did on my cards. Reporter: She's now speaking out warning others about the dangers of online dating. Simon, born Shimon, a 28-year-old convicted con man who served three years in Finnish prison for defrauding several women to fund his lavish lifestyle. When I'm reading the messages, I see how much talk there is about the banks. It's like, you're so stupid, you know? Reporter: Celia says she was lulled into a false sense of security by his grand romantic gestures and flowery declarations of love. I will support you, I will help you, we will lift each other, you're nice, you're cute, you're sweet, you let me do what I need to do and I really, really appreciate it. Reporter: For Celia the relationship started out innocently enough. This was the first time where I felt, oh my god, I really like him and it seems he really likes me back as well. You like the feeling of being liked. When do you consider yourself to be his girlfriend? I think it was maybe a month after that. Reporter: She says Simon told her his job as a diamond dealer kept him traveling constantly. They dated long distance. Their romance conducted via modern-day love letters in texts. Video messages. Voice recordings. I wish you a great and a beautiful and a successful and amazing day as you, kisses. Reporter: Simon stole away to London when he could, but more often than not he flew her to where he was, always alluding to an element of danger in his job that kept him away, jetting around constantly on private planes. How often would you see him on a weekly basis? I saw him like in London the next week. And that's when he started that he couldn't come back to London because of the 3s that he had been getting. Within a week he was already saying to you, I can't come back to London, there are threats against my life? But he could get me to where he was. Reporter: She says Simon claimed to be under constant threat from unknown, nefarious enemies, a hazard, he said, of working in the diamond business. There's nothing during this time that's making you think, this isn't real, he's fake? Oh, no. No, no, no. Good night, my love. I miss you so much. I can't wait to see you. Reporter: Celia says that Simon surrounded himself with people who helped perpetuate the myth, going so far as to send videos of himself and his board guard in the hospital after they were allegedly attacked. Soon another strange element to his story. She says he asked her to extend her line of credit to him so that plane tickets, hotels, and dinners would be booked using her name, keeping supposed enemies thrown off his trail. How do you go from being with someone who's presented as a very wealthy man, to someone who you now need to give money to? Protection. I know it's not right but he needed my name as a cover, he said. Protection from? His enemies, as he's calling them. You just believed him when he said that? I know it sounds so crazy. And I wish I could take everything back. It's more like when you have a bodyguard, why would this giant guy be with him if he didn't need the protection? Reporter: Celia says she relented because Simon promised to pay her back, but the repayments from Simon were nowhere to be seen, despite his us sister tense they were on their way. Emails that he needs to be able to just function for a week, it's just so much. It's never just a few thousand for us normal people, that is a lot of money, but for him it's not a lot of money. How could you have trusted him to take out that amount of money? Of course he has the money so he will pay me back. You didn't even think that it was a problem when you were taking out the loans because you were so sure that the money Apart from anything else, you loved him? Yeah. I think that's the hardest part of it. Like when I realized that he wasn't who he said he was. It was the love aspect, the person that I thought that I knew and loved, he had just done this in the most evil way. Reporter: Suddenly Celia's dream romance was crushing down around her. Two guys from American Express come to you. They say that's him, that's the guy. They told me they had had a long investigation on him already. And that I was a string of four, five women. I almost wanted to throw up. Everything just came crushing down at once. Reporter: Celia alleges that Simon was continuing to run the same scheme that put him in Finnish jail just a few years ago, using her money to fund his luxury lifestyle, and lure other women into his orbit, a cycle doomed to repeat itself. I had to be put into a psychiatric ward because of suicidal thoughts. I didn't see a way out. You lost your boyfriend, and not that he dumped you, he never existed. He was never your boyfriend. Reporter: Celia filed a report with the metropolitan police in London, who declined our request for comment. American Express told ABC they do not comment on open investigations. Meanwhile, Simon says he's in Panama, telling us via text he is innocent. There's nothing here, just a loan between friends that went south, she agreed to loan me money then she disappeared, not answering phones or emails or letters before we were able to pay her back, they used me for my life and got expensive gifts and everything, in other words, gold diggers. When I ask help they agreed to help and they know that I have some problems. I didn't run from no one, it's all fake news and lies. For now Celia remains in London trying to rebuild her life. I see a difference in myself when I talk to people. Maybe less naive. Much less, much less naive. Reporter: For "Nightline" I'm James Longman in London.

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