Is what a 23-year-old girl experiences—the emission of pre-seminal fluid (madhy) merely upon feeling aroused, hearing words of love, or seeing something that excites her—an obsessive-compulsive disorder or a reality? And does she need to change her clothes and repeat her ablution every time?

You must repent from romantic conversations with your fiancé and from watching lust-inducing movies and TV series, as they are forbidden by Islamic law. The cure for obsessive thoughts (waswas) is to ignore them. If you doubt that pre-seminal fluid (madhy) has been discharged, the default assumption is that it has not been discharged. Do not pay attention to mere doubt, because the default state is the continuation of purity. If you are certain that madhy has been discharged, then you must cleanse yourself (istinja’), sprinkle water on the clothes that it touched, and then perform ablution (wudu’). There is no need to change your clothes. There is no specific time for the discharge of madhy.