We have a mallard duck that has been laying eggs. It appeared she finished laying ans has been on them every day for a week in a half. She is in a very busy area of my yard, right next to our house and garage where we come and go. That hasn't seem to bother her,but we did have a lot of company over the other night and cars parked near her ( but not too close) . That was Tuesday night , Wednesday she was gone and has not been back. When she was staying on her eggs and then left for a short period, the eggs were always covered up, but now I can see all the eggs and I noticed one egg is away from the others ( out of the nest). Has she abandoned them? It turned cold yesterday and it is 32 this am. Should I cover the eggs up?

It sounds like the hen abandoned the nest. The eggs can't go that long without being incubated, so they are no longer viable. You can either leave the eggs for an animal to scavenge, or, since the nest is in a busy area of the yard, dispose of them in the trash. If you touch the eggs or nesting material, be sure to wash your hands thoroughly with warm soapy water.