I agree w/Ddawn. A hen goes broody when her hormones tell her to, regardless of what you may do.
I wanted to ask, though, what breed she is, if you know? Some breeds are much more likely to go broody, some rarely do.
Some that do brood may be triggered by seeing a nest full of eggs. The sight of the eggs can cause the hormonal shift, much as the sight of, um, certain physical features, can cause hormone shifts in humans.
Golf balls, wooden or ceramic eggs, (craft shops often carry these) even egg shaped rocks, or ping-pong balls, can be used, so you don't wasted your perfectly good eggs by leaving them for a non-broody hen.
You don't "stick then under her", though. Just put them in the nest, and wait. If she starts staying on the nest all the time, fluffs up and growls when you approach, and is still there when she shuld be going to roost, you have a broody hen. You can wait a day or two to make sure she's "setting tight", then swap out the fakes with real, fertile eggs.
Then mark your calendar for 21 days, and wait. Check under her every day or two so that if an egg breaks, you can clean up the mess, (before it starts to reek) put in fresh bedding, and put the rest back in.
If you had more than one hen, you'd need to mark/date the eggs, (unless you could separate them) but since you just have the one, there's no need to do that.
DO NOT keep adding more eggs later! Give her a batch of eggs, all at the same time, and let it be. Give her only as many as she can comfortably cover at one time, with none poking out anywhere.
If she's broody-type breed, you can start saving up her eggs, date them with a pencil, and when you get about 8 or so, depending on how many you think she can cover, start rotating out the oldest egg and replacing with a fresh one. (These eggs, kept at room temp, are perfectly ok to eat.) That way if she goes broody, you'll have fresh eggs to give her. (You do still have a roo, right?)