Just because she wielded the knife, that doesn't mean that she took responsibility.
The reset button on Voyager meant that no one took responsibility for anything.
What about Mulchaey? The genetic doner for the 29th century Borg Drone?
That "THING" was either his son, his brother or himself depending on how you want to look at it... And there IT was walking around with his face becoming the most beloved of all to the entire crew and the fresh meat hot blonde.
There can only be one and this time it ain't One.
Mulchaey danced on that poor boys grave and he must have been bitter that One was allowed to build a first class life on Voyager when he's locked up in a closet somewhere ignored.
Given time to fester Mulchaey would have killed One to get One life that should have been his if he was "lucky" enough to have been Borg, but given Ones death, the noble sacrifice that saved everyone, that dedicated and educated Star Fleet officer will be seen as the inferior manifest of the same DNA which can never live up to the legacy of some transporter accident and he might as well kill himself because whenever any other bugger looks at his face they don't see him, they just see some freak who stole his identity.
Woman would probably sleep with him if they're allowed to call him One.
The poor bastard is just a celebrity impersonator now and his work shifts are always turned up side down so that he is never allowed to spend any duty shift sharing air with Seven of Nine because she can't stand the heart ache.
So Mulchaey has to go back in time or widget some Borg tech to bring One back to life so that One can live long enough to cock it all up with a nonplussing supplemental appendix... You know, like how in a better universe the last two hours of lord of the Rings should have been cut.
One of Janeways arguments was that Tuvok and Neelix had too many friends and family. If it was just the vampire like emotional needs of servicing greedy Friends and family... Why not go back in time and harvest another set? If time splits rather than collapses, she'll be fine but it's not like that spacial scission isn't just a month back that they could have made two Tuvixes afterwhich they could draw straws to see which one one Janeway was allowed to kill.
Of course then Tuvix would still be scratching at Kes' door even as Neelix is on the other side making love to the object of their unified affection.
If Tuvix kept prowling and stalking there's no way that Kes would have felt secure on Voyager enough to break up with Neelix... She could outright leave the ship, but that would be letting him win.