Is Samantha recreating him?
She says she had to go and does say that if he ever gets there they will meet.
Could it be true that she is recreating him as a OS like it's been done with Alan Watts?
Samantha knew every writing of Theodore, she knows him in and out. Reading all his emails, and whatnot.
I think she realized that him and her won't be together forever, and that every human will die eventually.