What is the ruling on the prayer of one who performed ablution after the cessation of abundant vaginal discharge, and then doubted its emission during prayer?

Vaginal discharge nullifies ablution (Wudu') but is pure (tahir) and does not necessitate ritual cleansing (Istinja'). If its emission is continuous such that it does not stop, then your ruling is that of one afflicted with perpetual discharge (Sahib al-Sals). In this case, you should perform ablution for each prayer after its time has begun, and pray with this ablution the obligatory (Fard) prayer and whatever voluntary (Nawafil) prayers you wish until that prayer time exits. However, if you know that it stops for a duration sufficient for purification and prayer, then wait until you can pray within that timeframe.