Swamped

We could make it look like we're moving to board them. Start getting the planks ready, then make some excuse to get the sailors away. If she can get on a plank, the pirates won't have to come as close. That will encourage them to take the opportunity.

It takes a while for Resk to respond.

Okay, I'm telling two reliable sailors to fetch the planks and bring them to the deck. They know what's going on and they'll make up a convincing problem that makes 'em have to leave the planks unattended. Only part I'm not clear on now is how we make sure she knows we're making a move.

That's a point. It's likely she can communicate with the pirates. But they wouldn't be able to see the sailors leaving, and even if they did, they wouldn't know why. And with everything that's going on, getting the information to spread through the ship would be difficult - too many sailors have other tasks to deal with. Barely any are available to act as messengers, so they'd only be sent on very important missions.

So you need to either have a plausible reason for someone to run down here talking about the boarding plan, or you need some other way to encourage the warden to be on the deck on the right time. This is going to take some thought.