CONFESSION: When Bethany turned herself into the templars I was angry, I had wished there had been an option to slap her. I felt she basically spit in her family’s face doing that. They had made so many sacrifices to keep her safe and she threw it away like it meant nothing. What would have happened to their mother if Hawke had been killed in the Deep Roads. It made me so mad that the next time I played I killed her in the Deep Roads, though I did feel a little bad about it.
I believe what makes her turn herself to the Templars was two things: she thought she was useless when Hawke didn’t let her go to Deep roads and the fact Kirkwall is A LOT more dangerous to apostates than Ferelden.Source: dragonageconfessions