Speaking from the perspective of what makes an interesting episode... the writers wouldn't have wanted to make the decision more palatable. That's the point.
Janeway did kill Tuvix.
That should never be easy.
Janeway certainly doesn't think so, as she leaves sickbay with a look of resignation / muted (?) horror on her face.
That's the thing in the end: while some folks are passionately arguing that Janeway did the right, moral thing, that there is no reason to question her actions, I think Kate played it beautifully at the end.
Janeway knew that what she'd done was, at best, questionable. But she did it, took the responsibility, and she's the one who will live with it.
That brief pause and the look on her face outside sickbay spoke volumes.