If Oda does Yamato very dirty, at worst she will come to Kaido vs Luffy site as non factor.
Just like Franky was briefly there when Luffy was fighting Lucci but barely a factor. Or Usopp coming to distract Lucci as another non factor.
Luffy vs Kaido will be exchanging blows with advanced CoA and advanced CoC, Yamato coming there can only ends up getting stomped.
At least she can defeat Jack first before coming to rooftop and showing her DF.