3. After Tori gave Tris her Aptitude Test she found out that Tris was Divergent. She knew she had to warn Tris of the dangers so she didn't end up like Tori's brother. She couldn't bare to see anymore Divergents killed and the faction leaders have the audacity to say it was suicide. So the moment she told Tris to not tell anybody about her Divergence she wanted to tell her about her brother's story, how dangerous it would be, how Tris just needed to be an average faction member. But she couldn't tell Tris her brother's story right away, so she prepared to tell her if she chose Dauntless. She knew Tris would seek out answers, and eventually come to her for them. So all she had to do was wait, then she could finally tell the story of her brother's murder all because he was Divergent.