You need to understand this:
Fact 1: Carrot is 15, she is still a teenager who want to enjoy life to the fullest
Fact 2: Carrot has been THE representation of the mink tribe in anyway shape or form since their introduction (even in front of Inu and Neko in both the story and the meta).
Fact 3: Carrot is not a leader and was never represented like one
Fact 4: Carrot has been shown LOVING the sea and the wonders of the world to a CRAZY extent.
Fact 5: Carrot left once zou before
Fact 6: Carrot LOVES the strawhats
So.. Looking at those facts, let see what could happen:
1 - Creating a crew for herself?
Why would she do that when she can just hop on the Sunny again. Plus fact 3, Carrot is not a leader.
So.. No
2 - Joining a crew of minks on sea ?
Why would she do that when she can just hop on the Sunny again and join the one crew she loves. Plus Carrot has been THE representation of the mink, why would she settle to be just a number in a crew when she was the face of the mink tribe ?
So.. No
3 - Staying on Zou / Wano ?
Why would she do that when she is sure to have a much better time on the sea? Remember fact 1 and 5, she is like a teenager beside of a roller coaster and she already left once before. Her characterization is clear : Carrot will seek fun EVERYTIME.
So.. no
4 - Being captured ?
Why not, but it would be odd for someone to capture Carrot out of nowhere
So.. very unlikely
> So the only thing that make sence if we follow the characterization of Carrot and those facts is that Carrot will want to have fun again, Zou will not be enough and she will sneak again on the Sunny. Remember the words of Oda "my character are sometime acting by themself)
Carrot sneaking on the Sunny is just the most simple and logical outcome. In fact, Carrot would have 1 panel in the entierity of Wano and this take would stay the same: She will sneak on board.