Has she been broody for a while?
The thing with broody hens is that they can be pretty unpredictable, so these things are always risky. Sometimes it can go really well with no problems. Sometimes the hen won't stay on them, or eats the eggs, or kills the chicks - and that's with her own eggs that she's been on the entire time.
Yes, I've done this and had it work, but usually with a hen that's been on some kind of eggs or substitute eggs for a week or so already, so I know she's actually going to stay put. It's also important to have her in the place she's going to be raising the chicks BEFORE you try to put those eggs under her. Moving a hen and then trying this can end in a disaster. It's not a big deal with brand new eggs, but would be with chicks a week from hatch.
If she's been sitting and in a good spot, then I'd say you can try it. Maybe only put a few in there to start and keep the incubator running regardless, in case it doesn't work out. Just keep in mind that you may very well lose the chicks in the process, so if they're expensive or important eggs you may want to not try it.
I hope that helps!