Is the Nikah still valid if a girl is married to a man but her parents have prevented her from living with her husband for over 8 years without any valid reason?
Bismihi ta'ala
As long as the nikah was done, and talaq has not been recited, she is still considered married.
However, why would her parents prevent her from living with her husband. That is very wrong and must be solved immediately. Either she lives with her husband, or she gets divorced. It is unfair for her to be in this situation.
And Allah knows best