An foreign woman considers me as her son. What is the ruling on my khalwa with her?

It is not permissible for you to be alone with a foreign woman because Satan will be the third of you and will strive to lead you into the forbidden. The Prophet, peace and blessings be upon him, warned against entering upon non-mahram (definition) women, and mentioned that the first trial of the Children of Israel was concerning women. Therefore, you must distance yourself from the causes of temptation and abandon this relationship, and do not sell your religion for a worldly gain.