At this young age, since she treats people well, I wouldn't be too concerned about this. As you already are, continue to try to model an altruistic, "Golden Rule" approach to life. The capacity to be empathic occurs gradually over time, and judging by your daughter's reaction to those she knows, she does possess the capacity to be empathic and altruistic. Be careful not to go overboard, though. Simply respond to events and circumstances as they occur. In addition, while reading to/with her, depending on the situations that arise in books, ask her questions about how others might be feeling, what she might do in particular situations, etc. This type of vicarious learning can be quite helpful to a young child.
Thank you! I was very worried and I'm glad to hear that this falls in the "normal range".