That would heavily depend on what it was she was being proved wrong about.
Malina would be pretty angry. Yeah she's happy, but Malina knows that she's not someone made entirely of love. Of course, that's if she doesn't know about the girl who came before. If she knew what she was before, what she could have been, she would be happy... And she would hate that. She would keep it to herself, yeah, but there would always be that voice in the back of her head, scolding her for being happy Carmine was almost killed.
Titania doesn't have a great connection to Carmine beyond student and teacher. She's seen a lot of students come and go who've nearly died in the past, have families and friends killed or worse, or even never knowing their own families. This wouldn't faze he much. She would pity her somewhat, but that's it. If she knew of the girl that came before, she would find it was for the best. And nothing more than that.
Man, Malina is just racking up hate for Leo in this hypothetical world. If she didn't know if the girl who came before, she would confront Leo about it, visibly angry, and probably learn about the girl. If she already knew, she would be thankful for the Titan, though she would never ever ever ever let him know that. Not even a hint.
She would make sure that the source was correct before confronting Leo, if she didn't know the girl. If she did, she wouldn't do anything at all.
I mean time shifting is already a mega hax semblance so there's that. But she wouldn't be upset. Well, she would, but not on the surface. She would probably ask Rose what she is, but I know she should be asking is what is she wielding.