Honestly that's the part where I can't really symphatize with her because in the end she chose to come back because of her pride. I can understand that in the 1st timeline she felt alone and abandoned which is quite ironic considering the novel title ... as you said she could have gone back to Earth and lose her memories but for her that would have meant that she "lost" to Tia? Can't really understand her way of thinking but basically apart from wanting to take revenge on Ruve and Duke Zena she came back to "defeat" her (in what way I don't know maybe make people love her more?). Yes, he was never on Duke Zena's side. I don't really remember the details but he really wanted to help Tia but because he didn't have enough power and influence he couldn't do it directly, that's why the misunderstandings. In the 1st timeline I believe he revealed to Ruve that he was poisoned, even gave him the antidote and was one of the few people who tried to help him.