Dr. Main K. Al-Qudah responded to this issue as thus:

‘The existence of father as a Wali or representative in a marriage contract is one of the pillars required for the correctness of this contract. But if the parents are so abusive and reject any proposal or prevent a lady from marrying whomever she wants, although he is the right or qualified person to to marry the lady out, then she can complain to her local Imam and let him get involved and help her finding a solution to this dilemma.
Worst comes to worst; if the Imam is convinced that the parents have no valid reason to prevent her from marrying the one she likes, he can act as her Wali and let her proceed with this contract.’