It's not your turn yet...Jimjar and other NPCs still need to go then it goes. That last bit about it not being able to attack you is a hint of sorts...
Given the situation, we don't have a lot of options. If someone is able to hold Surana, like Derendil is holding me, then she might be able to grapple the beast, but given our precarious position, that could be death. I don't know what else to do!
Edit: It's always a bit cheesy to exploit the ability to split movement and attacks but it's something I've taken advantage of to make an encounter a little tougher. So it is something PCs can do sometimes too as long as we're not setting up attack conga lines...