There's no one answer to this question. Our evaluation of Rosemary's actions largely comes down to a matter of opinion. With that in mind, we will examine the opposing arguments that Rosemary was, and was not, justified in giving up her role as Receiver of Memory.
First of all, let's look at the arguments in support of Rosemary's decision. As Receiver of Memory, Rosemary had to experience a lot of deeply unpleasant stuff, memories of loss, loneliness, and depression. This would have been difficult for anyone to cope with, let alone someone without prior experience of any of these horrible things.
Under the circumstances, we shouldn't be too surprised if Rosemary couldn't handle all these disturbing memories and that she therefore felt that she could no longer continue in her role as Receiver of Memory. In the end, it wasn't her fault that she had to leave her position; it was the fault of the elders of the community for expecting her to deal with bad memories without being adversely affected.
In opposition to this, we might argue instead that Rosemary was wrong to quit as Receiver of Memory. The role is a very important one to the general stability and well-being of the community and confers a great deal of responsibility. It's a difficult role, to be sure, but it must be performed all the same. In failing to carry out her duties, Rosemary abrogated her responsibilities to the community and, in the process, diminished the standing of the office of Receiver of Memory.
The immediate consequences of Rosemary's deserting her post were damaging indeed for the community. In the wake of her quitting, all manner of unpleasant memories escaped into the community, leading to widespread trauma among those who experienced the horrible memories that Rosemary had found impossible to deal with. None of this would have happened had Rosemary remained as Receiver of Memory.