At worst, she would perish. At best, it would be a stalemate. Balance is frequently a theme in Zelda games, and Ganon isn't capable of balancing his power in a way that isn't destructive. The Triforce of Power can't be tamed without Link's Triforce of Courage added to the mix. Zelda knows her role and strengths and understands the severity of the situation. She can't take unnecessary risks, for if she fails, Link fails.