Vulcans understand calculated risk. It would be illogical to assume certainty was possible in any situation. What would be Illogical is for Samantha to assume that she didn’t have a positive impact on Naomi, and that Naomi wouldn’t be loved and cared for by the Voyager crew were she to die.
It would also be illogical to focus on what she cannot control (especially in an emergency situation) Tuvok is reminding her that she’s done what she can.