You don't have to blame anything on your hand. Take what you can work on and simply explain you had surgery and can't do the other work at this time. Take time watching and learning from the girls and help them with things you can do. If they are friends they will surely understand. Enjoy being with the group and make no excuses for your healing hand. Have a good time. I bet they will even offer to cut out your qullt for you to piece at a time when you can do it.
peace