The way I tell if a hen is broody and deserves hatching eggs is that she has to spend two consecutive nights on the nest. She'll probably spend practically all day on the nest too but it's the two consecutive nights that confirms to me that she is broody.
A broody hen should not be laying eggs but in the real world there are exceptions to everything. "Should" does not always mean "Ain't no way". I'm not sure if she is already firmly committed to being broody or not. Sometimes they are sort of maybe thinking about it instead of totally flipping to the broody side. I've had this go on for two weeks before they decide.
A broody hen should come off of the nest to eat and drink. I've had a broody hen come off the nest twice a day for over a hour each time. I've had one come off once every morning for 15 minutes. I've had some I never see off of the nest but I know they are coming off since they are not pooping in the nest.
The way I break a broody hen is to put her in a wire bottomed cage for 72 hours with food and water but nothing that looks like a nest. The air under her seems to help break her from being broody. 72 hours is long enough for most but occasionally I have to put one back in the cage for a while longer.
I'm not looking at your girl so I'm not sure what I'd do right now. I do not lock mine up until they are committed broody but I don't see any problems if you want to now. I don't think it is important one way or the other.
Good luck!