If mature boy and girl are match for each other (kufu) and the nikah is solemnized in the presence of two witnesses, the nikah will take place. But it is obscenity and shamelessness to marry in court without the consent of parents. It is unlawful to meet and talk to a girl whom you love. And when her father denied your proposal of marriage, you should let her off your mind and should not think of marriage with her. Act upon the advices of your parents and it is better to perform istikharah too. Try to follow the Shariah, in-sha-Allah you will be granted prosperity and blessing.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband