She accepts to ally with you.

From Create Your Own Story

The alliance is sealed quickly, and both of your ships sail side by side towards the island. As you approach it, darkness is beginning to fall. You drop anchor in a small cove with a sandy beach. A narrow peninsula separates you from another cove. A few minutes after dropping the anchor, you hear what sound like faint noises coming from the cove on the opposite side.

Another ship has dropped anchor.

Have your men and the female crew sneak to where the treasure is buried and dig it up by lantern and torch light

Wait until the break of dawn and investigate the other cove