I got eggs! Well, not the way I planned......

I have 6 girls, 4 of which are Isa Browns. I prepared their nesting boxes a couple of weeks ago, knowing that they could start laying soon. The girls are allowed to free range during the day, and their door opens automatically at 7 am. Today as I walked outside to go for a walk I heard some gentle cooing coming from the bushes next to the house. Upon investigation I discovered one of the girls sitting on a homemade nest and 10 eggs!!! I was shocked and elated lol. My plan is to shut the pen door tonight so they can't free range. Hopefully tomorrow morning she will use the nesting box I have prepared. My question is this. I have a couple of golf balls in the nests but can I put one or two of the real eggs in the nest to encourage her to go in there? Would that be better than the golf balls? I also don't know if the eggs are from one of the girls or several. It seemed to me that they were all waiting in line for their turn. Crazy birds! I love them and I HAVE EGGS!