If she really is incubating the eggs, chances are you will only get one chick(the first fertile egg she incubates properly) - she will then probably leave the nest a few hours after this chick got dry and any remaining fertile eggs will die. However, I wouldn't intervene either. Her biological clock might need some adjustment, but perhaps she'll get it right next time she tries ^^
On a side note, one of my button hens just hatched chicks yesterday - I haven't exactly been able to count the chicks yet, but there were 10! empty eggshells and two eggs left in the nest - of which I think one had actually pipped, but it was cold by the time I found it. I did put it in a nest with a hen that was till incubating though, just to give it a chance. Her incubation is going to get screwed up by all the chicks running around anyway, that's the bad part of having several hens in an enclosure. The chicks have no sense what so ever of who mom is, they see a button and then they go hide under it - and in the case of my hens at least, they just seem to accept this and help taking care of the chicks.