Does sexual fantasy about one's husband necessitate ghusl, and is it forbidden, given the presence of secretions without a feeling of detumescence or orgasm?

These fantasies are neither unlawful (haram) nor do they cause a woman to incur sin. However, one should not indulge in them. Rather, one should occupy oneself with what is beneficial in matters of religion and worldly affairs. These fantasies alone do not necessitate ghusl (ritual bath); ghusl is only required if thew woman is certain that semen (maniyy) has been discharged. If a woman is certain that semen has been discharged, ghusl becomes obligatory for her. If she is certain that it is pre-seminal fluid (madhiy), she must purify its location and perform ablution (wudu') for prayer. If she is uncertain whether the discharge is semen or pre-seminal fluid, she may choose and assign to it the ruling of whichever of the two she wishes.