All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Generally, a man's conversation with a non-mahram woman is permissible in case it is needed, provided that Sharee'ah controls are observed and everything that leads to temptation is avoided, and that talking to her is only as needed.
With regard to this case that he is responsible for, we recommend that he finds for this girl another girl to stand by her and help her solve her problem or guide her to some specialized advisory bodies and distance himself from temptation and its causes because the devil is in observation and seeks an opportunity to tempt him. Allah Almighty says (what means): {O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - indeed, he enjoins immorality and wrongdoing. And if not for the favor of Allah upon you and His mercy, not one of you would have been pure, ever, but Allah purifies whom He wills, and Allah is Hearing and Knowing.} [Quran 24:21]. Usamah ibn Zaid reported that the Prophet said, “I am not leaving behind me a more harmful trial for men than women.” [Al-Bukhari and Muslim]
Allah knows best.