"Surprised" conveys a milder and more general sense of unexpectedness, often with a positive or neutral tone, while "astounded" indicates a stronger and more profound level of surprise, potentially involving shock or awe. The choice between these words depends on the degree of intensity the speaker intends to convey regarding the unexpected event.
The difference between "surprised" and "astounded" lies in the intensity and nature of the emotional reaction conveyed by these words. In the given context, "surprised" suggests a moderate level of unexpectedness and may imply a positive or neutral tone. Julie's reaction to her grandma's impending visit is likely one of pleasant surprise, indicating that the news was unexpected but not overwhelmingly so.
Conversely, "astounded" carries a more profound and intense connotation. If Julie was "astounded" to learn about her grandma's visit, it implies a stronger emotional response, possibly involving shock, awe, or a sense of being deeply impressed. The use of "astounded" suggests a higher degree of surprise than "surprised," and the news might have been so unexpected or remarkable that it left Julie in a state of considerable amazement.