Does water retained in the vagina after washing, which exits after Wudu', invalidate Wudu', and is it pure given the difficulty of avoiding it?

When performing istinja' (purification after defecation/urination), a woman is only required to wash the external part of her private parts, which is what becomes visible when she squats to relieve herself. Washing the internal part of the vagina is not obligatory. If she washes what is obligatory and water exits the external part of her vagina after she stands up, her ablution is not invalidated, because it is considered to be like the external part. However, if she exaggerates and washes the internal part of her vagina, and water exits from it, then her ablution is invalidated by its exit.

It is stated in "Kashshaf al-Qina'": "It is not obligatory to wash as much as possible of the inside of a mature woman's vagina from impurity or ritual impurity (janabah). Therefore, she should not insert her hand or finger into her vagina; rather, she should wash what is visible, because the inside of the vagina is considered to be like an internal part according to Ibn Aqil and others. Thus, her ablution is invalidated by the exit of anything she inserted, even if without wetness, and her fast is invalidated by the insertion of her finger into it, but not by the arrival of menstrual blood to it, based on the premise that it is an internal part."

Based on this, if the drops exit from the external part of the vagina, then ablution is not invalidated. But if they exit from the internal part of the vagina, then ablution is invalidated by their exit. In case of doubt, the default is the validity of purification and the non-invalidation of ablution.