What should I do about a non-Muslim girl who intends to commit suicide, and should I inform her parents despite my fear of the consequences, knowing that I want to speak with her privately, and would leaving the matter be considered participation in the crime, "And who is more unjust than one who conceals a testimony he has from Allah," and how can I marry her?

You must invite this girl to Islam, explaining that Islam brings comfort and happiness and removes distress and psychological ailments. You can use the verse: "So whoever follows My guidance will not go astray, nor will he suffer. But whoever turns away from My remembrance – indeed, he will have a constricted life, and We will gather him on the Day of Resurrection blind."

You should forbid her from suicide and explain that her death as a disbeliever necessitates the Fire and that killing herself multiplies her torment. Inform her guardian or someone who has influence over her to prevent her from killing herself; otherwise, you will be complicit in her sin.

As for your marriage to her, it is permissible if she is a woman of the Book (Jewish or Christian) and chaste. Your invitation to her should be indirect, through another woman from your maharim or the wife of one of your brothers in faith. If she is a polytheist or unchaste, it is not permissible for you to marry her unless she embraces Islam.