Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
A man should not marry a girl whom one or both his parents dislike his marriage with her because obeying his parents in what is permissible is an obligation whereas marrying this specific girl is not an obligation. On the other hand, no parent is allowed to force his/her children to marry someone whom they do not want to marry because it may lead to an unsuccessful life or even to a divorce.
However, the man should try his best to convince his parents to accept this girl. In this regard, he has to seek Allah's help first and then the help of those who can convince his parents to let him marry the girl he is interested in. If they agree with his choice then he has to be thankful to Allah; otherwise, he should stop thinking about this girl and she should give up thinking about him too. Surely, Allah will grant each of them a better match.
We would like to draw your attention to two important matters:
1- Parents have no right to prevent their children from marrying at all or to delay their marriage without a legal reason. If the parents do so the children are not bound to obey them, especially if the children fear committing Zina.
2- There is no harm for the Wali to search a suitable match for the woman who is under his guardianship as Omar, may Allah be pleased with him, did for his daughter Hafsa, may Allah be pleased with her.
Allah knows best.