My uncle wants me to teach his daughter how to drive. I wear abaya but she doesnt& I've advised her. In this case would it be permissible for me to go out with her on the road and teach her, if she isn't doing proper hijab? If i say no, it may harm kinship.

May Allah reward your concern for your deen and your kinship. Teaching her to drive is itself permissible and a kindness. The question is her state when you go out together, and the scholars distinguish: if a woman goes out in open tabarruj — adorned or perfumed in a way that draws attention — then accompanying her in that is not permitted, because it is helping in the sin. Allah Jalla wa ʿAlā (the Majestic and Exalted) says, the meaning of which is: "and cooperate in righteousness and taqwā (piety), and do not cooperate in sin and transgression" [al-Māʾidah, ayah 2]. But the scholars also warn against excessive strictness: minor shortcomings are tolerated, with continued gentle advice. So look at her actual state: if it is open adornment before men, decline the lessons kindly and keep the relationship warm through other means; if it is a lesser shortfall in covering, teach her, keep advising with gentleness, and your duty of naṣīḥah is fulfilled — her covering remains her own account before Allah.