how did sarada find out boruto is innocent

Sarada found out Boruto was innocent because she had direct personal reasons to trust him, then later the story made her one of the few people who resisted the memory rewrite and still believed the truth about him. In the current Boruto storyline, that’s why she keeps defending him even when everyone else thinks he’s the enemy.

What happened

• Before the time skip, Sarada already had a strong bond with Boruto and had seen enough of his character to believe he was not the kind of person who would betray the village.

• After Eida’s power changed everyone’s memories, Sarada was one of the rare people who did not accept the false version of events, so she continued to insist Boruto was innocent.

• That is also why she pushes so hard when speaking to the adults in Konoha: she is not guessing, she is acting on what she knows to be true.

Simple version

If you want the shortest answer: Sarada didn’t “discover” Boruto’s innocence through a single clue alone; she came to trust him personally, and then she remained one of the few who still knew the truth after the reality shift.

In context

A lot of fan discussion frames this as Sarada being emotionally and morally certain long before everyone else caught up, which is why she becomes so important in Boruto’s defense.