Is it obligatory to perform ghusl again after a sticky white fluid is discharged following ghusl from semen that was emitted as a result of thinking about intercourse before Fajr?

If a woman doubts whether what exited her body is manī (seminal fluid) or madhī (pre-seminal fluid), she has the option to choose between considering it manī, in which case she must perform ghusl (ritual bath), or madhī, in which case she must purify whatever it touched of her body and clothes. This is the view of the Shafi'i school. A Muslim woman should not dwell excessively on such thoughts.