That depends in her because it would be HER wedding.

If she is grateful enough, you'll get to walk her because you would have been her real dad all her life.

There is no written law that the bio that most be the only one who can walk her, its all just stupid wedding traditions.

If she grows to be a brat, and makes her bio dad walk her, then she doesn't see you as her real dad, and would be something for you to reflect on.