How can a former fiancée who committed a sin (doing things like married couples without penetration) and then repented from it deal with the problem of frequent, unconscious seminal emission due to remembering what happened, which affects her purity, prayers, and fasting, given her inability to tell her mother or go to a doctor without her knowledge?

To overcome negative thoughts, be sure to occupy yourself with what benefits you, and ponder the welfare of this world and the hereafter. Also, fast frequently.

The discharge that often exits is madhi (pre-seminal fluid), and it necessitates istinja (definition)' (washing the private parts) and purifying whatever it touched, and performing wudu' for prayer. Ghusl (definition) (ritual bath) is not required unless you are certain that mani (seminal fluid) has exited. If you are uncertain whether it is mani or madhi, then choose between the two. If you are certain that mani has exited, ghusl is obligatory, even if it happens repeatedly.