It's a group for 'female-born' and questioning, if you don't have a name ready, then you don't have a new name ready yet. You can pick the first that comes to mind when you're there and tell them it might change soon though 'cause you haven't really decided on it yet. But you'll let them know when you do.
That's fine, all of them will go through the process of deciding on their name, there's the chance some of 'm there might still go by their female names (or maybe unisex names they want go by during transition).
Ah, and don't sweat it alright.

You'll be fine.
Though looking at the time now, I might be a little late, I'm not sure what time your group-thing is. Enjoy anyway!