Wa alaykum salam wa rahmatuLlahi wa barakatuHu,

Regarding vaginal moisture, or in Arabic رطوبة الفرج, as mentioned it does nullify the ablution when it exits. When it comes from what is exposed when a woman squats (i.e. where it is obligatory to wash in a ghusl), it is pure. When it comes from where the male part reaches during intercourse, it is pure. When it comes from behind where the male part reaches during intercourse, it is impure. (Tuhfat al-Muhtaj v. 1, p. 300-01) If she doubts regarding where it came from, then it is assumed to be pure.

And Allah knows best.

Shafiifiqh.com Fatwa Dept.