In the end, Juliana gave up on the idea because she knew Timothy would not believe such an inconceivable thing.
Perhaps he would even resent her and attack her if he thought she was trying to impersonate Miranda.
That would be disadvantageous to her.
Juliana said to Timothy, "Whatever happens to you, I don't think she wants you to marry anyone else."
Timothy's voice got even colder, "Get out and don't make me have someone throw you out!"
What did Juliana know as an outsider?
He didn't want to marry Wendy but... Wendy's heart was donated by Miranda.
Miranda's last wish left behind was for him to marry Wendy and be good to her for the rest of his life.
Miranda had said that if he did not fulfill her last wish, she could not die in peace and would never want to know him again in her next life.
Even if it was against his heart, he would still fulfill Miranda's last wish.
Timothy's attitude let Juliana give up the idea of explaining her identity to him and she turned to leave.