Hi. You did not submit the specific excerpt from "Incident at Valley Forge" which makes it impossible for your question to be answered accurately. However, if we consider the entire text, we can see that Marta Washington, in general, acts in a very optimistic way.
That's because "Incident at Valley Forge" seeks to present what happened in Valley Forge during the American Revolution, while George Washington led the fighting force against England's army. In this text, Marta Washington is very optimistic, certain that everything will go well for the continental army. She believes that they will achieve victory and that everyone will return safely to their homes.