السلام علیکم ورحمة الله وبركاته
There's a new Muslim convert sister who is getting married. Her family have not accepted Islam. For her nikah, she's sending a Muslim man to represent her as her wali for the عقد النكاح. Is this the correct method and will the nikah be valid? Or does she have to go to the masjid herself?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
In the Hanafi Fiqh, a mature woman can act independently in her marriage based on the hadith: “A woman has more right to herself than her guardian.”
Thus, it would be a valid nikah for her to be married without the presence of her father in this case especially. According to the Hanafi jurists, a non-Muslim cannot be a guardian over a Muslim woman in the case of marriage. Therefore, it would be permitted for her to perform the marriage on her own behalf in such a case.
Note: This would be sinful to do in the case where there is a valid Muslim guardian available to the woman. The other schools of thought have considered such to be an invalid marriage, in the case a woman does have a male Muslim relative as her guardian.
Also, in many cases such as the one mentioned above, it is best to have a local scholar involved throughout the process and to even have the Imam act as a general guardian for the Muslim woman. This would be best to protect her from unseen harms and to repel any unsuitable prospects.
Al-Fatawa Al-Hindiyyah, Volume 1 Pg 316
Only Allah knows best
Written by Maulana Nabil Khan
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Sahih Al-Muslim 2638, Authentic