Should the questioner stop interfering in her engaged friend's life based on her mother's advice, or should she continue to involve herself and her friend in solving their problems, knowing her good intentions and the difficulty of abandoning them?

What is obligatory upon you is to sever ties with your friend's fiancé, because he is a stranger to you, and it is not permissible for a woman to establish a friendly relationship with a strange man. Obeying your mother is obligatory if she forbids you from accompanying your friend. Engagement is merely a promise of marriage, and the fiancé is a stranger to his fiancée until the legal contract is concluded, so it is not permissible for her to speak with him except to the extent of need, while observing the Sharia guidelines.