Some turkey hens love to set eggs and others could care less. If she's a setter you can leave the egg and she'll lay a nestful and try to hatch them but your hatch rate isn't going to be nearly as good as an incubator, and possums, rats, etc. will steal the eggs during their last week of incubation. I let several hens set eggs last year and got so frustrated that the eggs that were almost due to hatch would disappear! I did get a few poults but then some of them disappeared also. I got 90+ percent hatch rate last year with turkey eggs from my cabinet incubator, as long as I put them in the day they were laid. (I dated them and was putting eggs into lockdown and hatching poults every day through the summer.)