What is the ruling on a woman speaking with her fiancé about sensitive matters that result in fluid discharge, and does this fluid necessitate ghusl? And how can one repent from this and get rid of the accompanying fantasies?

The suitor is a stranger to his fiancée before the marriage contract (aqd). You must repent to Allah for the unlawful speech that occurred between you, by abandoning the sin, regretting it, and resolving not to return to it. To overcome the abundance of sexual fantasies, I advise occupying your time with beneficial matters while seeking assistance from Allah.