If you only have 10 hens altogether (including her) then she is still laying and usually when a hen is truly broody, while they may lay for a day or two in the beginning, in my experience they stop laying after that and don't lay again until a couple of weeks after the broody stage ends. Also, I would think she would be laying on at least her own egg. Is she fluffing up and pecking at your hand if you try to reach under her? Try removing her from the nest, (if you are uncomfortable with this because you don't want to get pecked, wear long sleeves and gloves and don't hesitate when picking her up, just reach in and scoop her up) move her as far away as possible, then watch to see if she goes right back to sitting on that nest. If she is truly broody, this will not deter her even if you do it several times in a day. Also you can pick her up and look under her belly. If she is broody, she will have pulled out the feathers so that her skin is in contact with the eggs. Her belly will feel warm to the touch.
As far as putting real eggs under her, if you are wanting her to hatch them, then you can put as many eggs under her as will fit and you are comfortable with hatching. (or losing depending on if she is really broody or not) I think for a first time broody you would not want to go overboard on the number of eggs. Maybe 6-10 depending on how large of a hen she is.
If you do decide she is broody and you are wanting to hatch some eggs, It is a good idea to have her seperate from the other hens. She will need food and water close at hand as she will not go far from the nest. After the chicks hatch the other hens may not treat the chicks well and the broody hen may or may not be able to stop them from killing them.
You will want to put a light pencil mark on the eggs you put under her and you want to put them all under her at the same time so they will hatch close together. If you find more eggs under her at any time during the brooding you should check them for the pencil marks and if they aren't marked then take them out.
May I ask why you have ceramic eggs in the nest box?
CJ