So first of all, in a ship sounds like she has been kidnapped therefore its a weird sentence.
Secondly on a ship would be "a hajón"
Also "hajó" can be "boat" and "ship" as well
It can also be "hajóban", on a smaller vessel, like a sailboat. But "hajón" is definitely more common.
Why not use sincs
Why no longer "too" for "is"?