Praise be to Allah.
The discussion on such discharges focuses on two issues:
1 – Is it taahir (pure) or naajis (impure)?
The view of Abu Haneefah and Ahmad, and one of the two views narrated from al-Shaafa’i – which al-Nawawi classed as correct – is that it is pure. This view was also favoured by Shaykh Ibn ‘Uthaymeen, who said in al-Sharh al-Mumti’ (1/392):
If these discharges come as the result of intimacy then they are pure, because they are not the waste products of eating and drinking, thus they are not urine. The basic principle is that there is no impurity unless there is evidence that something is impure. Because a man is not obliged to wash his penis if he has intercourse with his wife nor to wash his garment if anything gets onto it; if it were impure then the maniy (sememn – which is pure) would become impure (through contamination with these discharges).
See al-Majmoo’, 1/406; al-Mughni, 2/88
Based on this, she does not have to wash her underwear or change them if these discharges get on them.
2 – Is wudoo’ invalidated as a result of these discharges or not?
The view of most of the scholars is that this does invalidate wudoo’.
This is the view favoured by Shaykh Ibn ‘Uthaymeen, who said:
Anyone who attributes to me the view that this does not invalidate wudoo’ is not correct. It seems that he understood from my words that it is pure and does not invalidate wudoo’.
Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen, 11/287
And he also said (11/285):
With regard to the belief of some women, that (these discharges) do not invalidate wudoo’, I do not know of any basis for that except the view of Ibn Hazm.
But, if a woman experiences this wetness constantly, then she should do wudoo’ for every prayer after the time for the prayer begins, and it will not matter if this wetness if discharged after that, even if that happens whilst she is praying.
Shaykh Ibn Baaz (may Allaah have mercy on him) said:
If the wetness described happens continually, most of the time, then every woman who experiences that must do wudoo’ for every prayer when the time begins. This is similar to the case of a woman who suffers from istihaadah (ongoing non-menstrual vaginal bleeding) or one who suffers from urinary incontinence.
But if this wetness only happens sometimes, and is not ongoing, then it comes under the same rulings as urine – when it happens it invalidates purity, even during the prayer.
Majmoo’ Fataawa Ibn Baaz, 10/130
See also question no. 37752
And Allaah knows best.