Is it permissible to marry a Shia girl who was previously a convert from Wahhabism without the approval of her father, in order to avoid committing a sin?
Bismihi ta'ala
It does not matter what madhhab or ideology the girl's father may be, her family should absolutely be involved, and her father must give consent for the marriage to be valid. Unless, of course, she meets the requirement of "balighah/rashidah".
And Allah knows best