Hi again and congratulations on the chick. Fingers crossed the other one hatches today
No she can't incubate eggs whilst looking after a hatched chick. She will either abandon the new eggs or neglect the chick, so definitely remove them.
The way it's supposed to happen is that a hen lays a clutch of eggs in a nest one day at a time and then she goes broody and stops laying and starts incubating them. That way, all the eggs start to develop at the same time and they all hatch within a day or two at the most, of each other. The chicks can live off the absorbed egg yolk for 48hrs before they need to eat but the hen then has to leave the nest with them and start teaching the chicks how to feed and drink and dust bath and everything else they need to learn. Unfortunately in an enclosed run and coop, there are limited options for nests and other hens will almost certainly lay into her nest either whilst she is off having a leg stretch and relieving herself or even climb in there with her and lay an egg. This is why it's important to wait until a hen is obviously broody and then mark the eggs you want her to hatch and give them to her. Then any extra eggs can be easily recognised when you check the nest and removed each day and eaten as normal. Allowing other eggs to be added to the nest willy nilly is just a waste and even poses a risk to the eggs that were originally set. Broody hens that free range often make a sneaky nest in a dark quiet place somewhere that the other hens don't know about so that they only incubate their own eggs.
If you have another broody hen you could take out the new eggs assuming you can identify them, mark them and give them to her but if they have already been incubating for a few days, you would be well advised not to give her any others and remove any new eggs that get laid into her nest.
I assume you have chick crumb available for the chick to eat. It will not do any harm for the mother hen to also eat chick crumb, but you don't want the chick trying to eat layers pellets at this early age as it doesn't contain enough protein and too much calcium and the pellets are too large although you will see the broody hen breaking them down for them with her beak if they do have access.
Fingers crossed the other egg hatches soon, so that you have two grandchicks!