What should I do or say to my niece regarding the following?

My brothers oldest daughter heard that he and I are going to Mexico March of next year. She said she wanted to come with us but it’s what or how she said it that pissed not just myself but my brother off too.

See the trip is for a medical procedure that my brother will be getting done so since his Spanish is not that great he wants me to come with him.

He spoke to his eldest today (who by the way isn’t inviting him to her high school graduation because of some reasons that are way too long to explain) and she heard about the trip. And then she said “oh can I come? I really want to see my aunt Kay, I haven’t seen her in a long time and I want to spend time with her, and we can go to such and such places (trying to make a vacation out of it) so my brother had to tell her no.

Anyways I know she’s doing purposely to hurt him and I’m getting tired of being the one who’s name is dropped to hurt him. To say that she’d rather see me than her dad is just plain mean. If she really doesn’t want contact with him why is she ok seeing him just to see me? Idk it’s weird. I’ve noticed she’s mastered manipulation beyond what her mother’s skill was.

So I don’t know if I should say something to her about it or not, because I know she will call me to try and get me to encourage my brother to bring her along.