What is the ruling in Islamic law regarding withholding useful information from a close friend who has withheld similar information from me?

If your friend asks you to teach her some of the Islamic sciences or beneficial knowledge you possess, it is your duty to impart it to her and not conceal it from her. This is due to the severe warnings against concealing knowledge, such as Allah’s saying: "Indeed, those who conceal what We sent down of clear proofs and guidance after We made it clear for the people in the Scripture - those are cursed by Allah and cursed by the cursers," and the Prophet's (peace and blessings be upon him) saying: "Whoever is asked about knowledge and conceals it will be bridled on the Day of Resurrection with a bridle of fire."