Sheikh `Abd al-Wahhâb al-Turayrî, former professor at al-Imâm University in Riyadh
If this wet substance is clearly discernable by her as the liquid that she discharges upon sexual climax, then she is obligated to perform ghusl. Otherwise, it is only some other vaginal exudation, and she does not have to perform ghusl.
And Allah knows best.
Source: Islam Today