Of course she can!Can she just raise them?
Of course she can!
You need to be aware of a couple of things. First, she might not be a great mom. That's a risk with an unproven hen but problems are rare. Second, other hens might not welcome her brood. If she's high-ranking in the order, that improves the chances that she'll do fine defending them. Some folks will take the sitting hen and her eggs and move them to a separate location. Not everyone does, though. Third, chicks shouldn't eat layer feed. The whole flock can eat grower feed if you provide a calcium supplement. It can be as simple as a cup that you keep full of oyster shell attached to the wall. If you separate the hen with her brood, she doesn't need the calcium since she isn't laying while sitting or raising chicks. You can simply give hen and chicks chick feed. HTH!
Oh, and you can skip the heat. She'll keep them plenty warm.