What is the ruling on a woman uncovering her face and speaking on the phone with a male relative who is not a mahram? And is it permissible for her to do so under the pretext that he is a relative?

This sister and her relative, who claims to be righteous, are opening a door to temptation (fitna) and sin for themselves through this relationship. They must be advised and guided with gentleness and wisdom. They should be reminded of Allah's boundaries and what is forbidden (mahārim), especially since kinship increases responsibility and necessitates safeguarding the relative from what is unlawful. The door to temptation with relatives must be closed because people tend to be lenient with them; indeed, the Prophet likened the in-law (hamū) to death. It is permissible for a woman to sit with her relatives under certain conditions: complete hijab (definition) and the absence of any suspicion. Gentleness must be used in advising, along with wisdom and good counsel. Advice can be hinted at without direct confrontation. If hinting does not work, she can be confronted gently, focusing on the status of modesty (ḥayāʾ) and the warnings against uncovering the face and intermingling (ikhtilāṭ). She should be reminded of the stories of those who fell victim to intermingling. Her mother can also be contacted to advise her.