I think it was absolute important for the Camara to pan over to Leia as Rey remarks she sees “light” for so many reasons.
Leia Organa has been fighting wars and oppression for her entire life. Her biological father turned to the dark side, her biological mother died after democracy did and the parents who raised her were killed by a weapon of mass destruction thanks to the enemy she had been fighting since she was old enough to know better.
Not once has she ever gave in. Even with the threat of her home planet being destroyed; Leia still lied to protect the secret location of the rebels.
She was tortured and she broke out, and continued that war for years to come. When Han was kidnapped she didn’t give up in rescuing him. When Luke revealed their true heritage she embraced the truth and continued to fight on.
She won; but there was still many wars to face.
Flash forward to the current era. Her son has fallen to the dark side like her father. Han ran away from his troubles; but Leia continued on the fight against the darkness. Against the First Order; a symbol of oppression and darkness.
Much like the empire before them.
If anybody symbolises “the light side”; it’s Leia. She’s always been the light in the darkness, the person who not once gave up. She’s still carrying on strong even with the knowledge that her own son killed his father. She broke away from the New Republic to lead the Resistance because it’s all about priorities here. It was the idea of Darth Vader corrupting Leia to the dark side that drove Luke to fight him.
Much like her mother before her, Leia is a firm believer in democracy and freedom; and I think the stylistic choice to have her represent the light was truly amazing and probably the best thing to come out of the trailer.