That sounds what you want, not what Yamato wants. Granted she will die for Momo, but that's because as she is now, she isn't free and wants to defeat her father... Once that's done, she'll have nothing tying her down.
Yamato is already free. Yamato herself said in chapter 985 that the shackles were the reason she wasn't free. So she makes it clear that she is already free even though she is still in onigashima. So leaving Onigashima had nothing to do with being free but rather leaving a place whenever she wanted without being forced to stay in one place.
I see it differently. Yamato now has a reason to stay in Wano to protect Momo and Wano. I doubt Yamato would leave Wano to the world government. That would be a contradiction to the Kozuki family and Oden.