Take a few eggs and see if she wants them. I'd keep a couple in the bator until you're sure. If she's going to set- sneak the rest under- preferrably at night. If she hatches them, she will most likely accept them. Make sure you don't give her more eggs than she can handle. Also- give her a sheltered place that other hens won't be able to lay in her nest.
How far along are the eggs you are incubating? The hen will have to be broody for more than a few days in order to accept chicks as a rule. A few don't seem to care, but most will have to have been broody for a couple of weeks.
If you are going to be brooding some chicks anyway, I'd suggest you just keep the eggs you've already started, and give the hen a few fresh eggs to deal with. Especially if it is a first time hen you really don't know how she would react. Just my opinion.