An OEG bantam is a breed that is likely to go broody, but you cannot guess when she will actually go broody. It may be months or years, if ever. Leaving several eggs in the nest is supposed to help, but it is no guarantee.
What I would suggest is to put fake eggs in the nest and take out the real eggs. Golf balls, wooden eggs, plastic eggs all work great. I would not leave the real eggs in the nest. They can attract predators like skunks, rats and snakes. They are more likely to get broken. It is best to remove the eggs daily.
Set up a rotation with the eggs that are being laid so you keep however many you want her to hatch, but use the old ones and always keep the newest. You can write the dates on them with a sharpie or black magic marker or just keep them in an egg carton in a specific order. I'll include a link to a Texas A&M site. It is about incubation but it tells you how to store and turn eggs in preparation to incubation. This is necessary whether you use a broody or an incubator. I'd store them at room temperature. I know this site recommends some place a little cooler but most of us have great success storing the eggs at room temperature.
I'd also suggest candling the eggs you are keeping for her to hatch. You are looking for eggs that have cracks or other weaknesses so you don't put them under her.
http://gallus.tamu.edu/Extension publications/b6092.pdf
I'll also incude a link on storing eggs for human consumption. It should make you feel better about leaving themout at room temperature.
Storing Eggs
http://www.motherearthnews.com/Sust...ggs-a-Year-or-More-Without-Refrigeration.aspx
By the way, the eggs are probably fertile. The only way you can tell is to crack one. I'll give you one more link. This one shows what a fertile egg looks like when you crack it. If one is fertile, they all probably are.
Fertile Egg Pictures
https://www.backyardchickens.com/forum/viewtopic.php?id=16008
Good luck!
