User blog comment:ArthurMerlinLancelot/"He is your destiny, and he is your doom"/@comment-4892425-20121225112528/@comment-5910979-20121226093701

She had little to no choice imo. She had a guardian/father who hated and despised magic and for all she could assume, he would've executed her on the spot if he found out. Then to have her most trusted friend at the time (Merlin) betray and try to kill her would make anyone cold, hateful and distrustful to him and anyone else she might've called friend. With Merlin turning his back on her, she had no one to turn to then except Morgause (her only known living relative at the time, and fellow magic user).

Running away to another land where magic is welcomed wouldn't have helped her either imo. Uther had Arthur and his knights searching endlessly for her for over a year - they would've found her and dragged her back to a kingdom where her kind is hated and persecuted and where she would've remained living in fear of the day she'd get caught and executed, or of another of her friends betraying her.

Her original goal wasn't to take the throne, but to get rid of Uther. It wasn't until after she learned another deeper betrayal (the lie of her parentage), and with Morgause's persuasion did she want the throne because it would've given her a better position to return magic. Her constant attempts to take the throne was because Arthur never lifted the ban towards magic which made her: obsessed, cruel, crazed/evil and revenge driven.