I would say that sometimes a hen will be friendlier to her offspring after weaning. In the past I had two hens who brooded chicks at the same time and even more than a year later, the hens still prefer the chicks that were theirs over the chicks that were mothered by the other hen.
To say that they forget them completely is wrong, I think. Chickens have very complex social relationships that are not just bound by the pecking order. For example, siblings raised together will usually prefer each others company to that of other chickens. The mother hen has to reject the chicks at some point for their own good so that they can be independent and for her own good so that she can get back to egg laying etc, but that doesn't mean they forget what happened. They have very long memories. It depends on the personality of the hen somewhat as well. But in my experience a mother hen will not stay very close to her offspring in the way that sibling chickens sometimes remain very close.