After the battle with Echo and Gal (which was their last) Echo defeated Gal and Gal (possibly) fell into disrepair and sat exposed to the elements, when you axed Leslie, the next day she wondered outside and found the remains, she took them back to her place and thought about something, she thought that she could get recognition back again so she made Gal a suit, looked in the mirror after doing and she said to herself: “No more Leslie, Gal is now my name! And I will find Mason and give him the fight he needs!” Put on the helmet and off she went (correct me if i’m wrong on the battle between Gal and Echo)