Hi, I just wanted to say that Nova doesn't come back to the present in the Christmas AS, Midori is the one going to the future.
Which is why Nova is sad and lonely because the future is... grimdark for the lack of a better word.
It contrast with how the present Rebel army treat her in the Summer 2018 AS, they summoned her for the sole purpose of cheerleading the troops.
Also Midori does more than just giving her hope, she literally give her a reason to actually live and fight rather than just listening to Future Vita's orders and die a meaningless death on the battlefield.
Ironically, if she does manage to save Vita from becoming a murderbot, it is very likely than she will also delete herself from existence.