If a girl has married against her parents will, someone was the wali of her nikah but her father was not the wali of her nikah, though her father is alive. Is her nikah valid or she has to go for a second time nikah?
When girl or boy reach the age of puberty then the wilayat [guardianship] of father is not necessary rather they are independent for their nikah. It is mentioned in Tirmidhi:
الأيم أحق بنفسها من وليها.
In the question mentioned above when the girl allowed for her nikah willingly and later on the boy accepted it in front of two witnesses then nikah was done. There is no need for fresh nikah.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband