I'm gonna make a prediction... NOT THEORY!!
Like the new category that Aurora made, says...
Kind of stolen speculation but it's mostly for those that come only here for discussions :D
After the revelation of Pudding being evil, there are still things that don’t add up and I mean Pudding's flashback of Lola.
Some believe that there’s some good in Pudding, she looked up to Lola, and maybe she wants to be free of Big Mom’s control, same as her sister, but I’m not thinking in that direction, I don’t think that there’s a single bit of goodness in Pudding.
So the speculation is...
Pudding hates Lola and she was responsible of destroying Big Mom’s dream.
Lola’s marriage was going to make Big Mom the pirate king, but why did she choose Lola to be the daughter to give her that title? That’s such a huge honor, isn’t it?
The answer is simple... Lola was Big Mom’s favorite.
The little Pudding envied Lola and wanted to be in her place, that’s why she was so proudly telling Reiju that she’s Big Mom’s favorite.
Note that VIZ translations shows Pudding saying “she’s mama’s favorite” NOT "one of mama’s favorite”.
Little Pudding convinced Lola to run away, probably by manipulating Lola’s memories, making Lola refuse the wedding, and thinking that mama will forgive her as if she doesn’t know mama. Basically forgetting Big Mom's true face (the REAL angry one).
But when everything was going smooth for Pudding, Nami came. And when the maid told Pudding that Nami is Lola’s friend, Pudding knew that Big Mom will make Nami tell her Lola’s location and what she did would have been revelead, making Big Mom go for her head.
So Pudding went out of plan made by Big Mom and told Luffy and Nami the things she told them.
--->( This part below is kind of off to me, but I'll post in anyway ) ...
She wanted to motivate Luffy and Nami to escape, so she will never be exposed, and that’s why she whispered, because Opera knows that Pudding isn’t supposed to say that.
Pudding wasn’t sure that Luffy and Nami are capable of escaping on their own. So she needed someone to help them.
No, it’s not Jinbei but Sanji.
So Pudding went and shot Reiju, waited for Sanji to come, so he will know that Big Mom doesn’t intend to keep her promise.
Knowing that Sanji is out of choices, If he told his family, they won’t believe him, thinking that he only wants to stop the wedding, and Sanji can’t escape WCI. So he will sure go help his nakamas.