I know a girl, she has been married to a person whom she dislikes. She was not willing to marry him. I want to know is her marriage void ?

If she agreed at the time of Nikah then her Nikah is valid. Now my humble request to all youths is that it’s true they have ambitious nature and they always feel that what they have decided is correct but in few cases we have give much more importance to our elders because they have more experience than them. Also Allah (swt) gives much more rewards if any how one of the spouse is not behaving well to the other so we have many example like Lady Asiyah( wife of Firaun) Allah (swt) has made her as an exemplary woman for both men and woman but you see how her life was. Can anyone imagine the cruelty of Firaun and when a lady bears all those pains and keep her faith strong and keep her modesty then obviously Allah ( swt) will reward. So please now tell to her to manage with her current situation because if for God forsake the issue would lead up to divorce then many families will collapse and they will face many problems both socially and psychologically. Rely on Allah (swt) by passing time everything will be settled. There are hundreds of example we have in our society where girl married against her wish but after that everything became normal.
We have leave some affairs on Allah (swt) and then we will see. He creates love and affection in the hearts of bride and groom not us. So don’t worry.