Now lets settle this! Tsunade willpower vs Tsukiyomi.

[know it all]

Are you kidding? Tsukuyomi is unbreakable unless you're one of a select few who have the unique ability to break the tsukuyomi of certain people. Example: Sasuke v. Itachi

End result: Tsunade would get one-shotted.

 

[Shadow Phantasm]

Tsunade would be a broken shell once Tsukiyomi finishes.

 

[Kurama999]

As Itachi himself said (to Naruto) that every jutsu, there is a weakness.
Tsunade had the understanding of this Tsukiyomi, else how could she healed Kakashi.
She could knew how to prevent, and not to get caught by Itachi Tsukiyomi.
If Itachi did intend to kill, he could go ahead.
It is up to the user to determine how long.