Is ghusl necessary after the emission of a transparent fluid when conversing with her fiancé, or is changing clothes sufficient, knowing that she sees a white discharge on all days?

There is no blame upon a woman for seeking a righteous man for marriage, within the bounds of propriety and Islamic law. However, it is not permissible for her to be in a relationship with him before the marriage contract, as he is a stranger to her.

It is necessary to ascertain the man's righteousness and consult those who know him. Then, perform Istikhara (prayer for guidance) before agreeing.

As for the fluid that exits when speaking with a young man: if it is maniyy (seminal fluid), ghusl (ritual bath) is obligatory. If it is madhiy (pre-seminal fluid), ghusl is not obligatory, and it suffices to wash it off the garment. The white fluid from vaginal secretions nullifies ablution and is ritually pure according to the most authoritative opinion. If its discharge is frequent, the woman is in the ruling of one with istihada (non-menstrual vaginal bleeding), and she should perform ablution for each prayer.