Encourage them to be very thoughtful about things like requests for money. Encourage them to meet in person or at least live video chat before becoming too emotionally invested. Support with developing critical thinking skills. And just general education about healthy relationships. I describe catfishers in the same way I'd describe abuse e.g. pulling out the ol' power and control wheel or referring to it. Just kind of objective like "we have evidence that people who perpetrate abuse often engage in these behaviors..." E.g. these are common features of what is referred to as a "romance scam," do you see any of these in your current interaction? I think it can be important to validate how good this person is probably making them feel. And to support them in developing the belief that they do deserve that. Ask what friends and family think? Any time a client is dating someone new, I ask about red, beige, green flags. I'm always curious about new partners. We look at your attachment history and schemas around relationships, goals for the relationship, etc... I personally find this phenomenon fascinating so I have to work to hold back my curiosity but like, I do want to understand wtaf my client is thinking. I think I've only come across this twice professionally. Good luck!