Forgive me for putting my 2 cents in, but isn't
Newdoria's effect a graveyard effect? The card says it has to be sent to the graveyard. DD Warrior Lady's effect states that it happens right after damage calculation, which would be before monsters are sent to the graveyard, and before
Newdoria's effect even activates in the first place.
This has nothing to do with mandatory vs optional -
Newdoria must be in the graveyard for its effect to activate, and since it never gets there, its effect never activates. There is no "chain link 1 and 2" and no "mandatory vs. optional."
Even though FLIP effects (like
Fiber Jar) would resolve between the "calculate and apply damage" and "send to graveyard" parts of the damage step,
Newdoria is NOT a flip effect. Its effect does not happen until after the "send to the graveyard" and long after DD's effect activates and resolves.
Not sure why everyone is making it more complicated.