My brother and I were traveling, and my girlfriend said she didn’t need to worry about her. Was she afraid that I would worry about her?

It depends on the tone of your girlfriend's words. If her tone is unhappy, then she probably doesn't want you to leave her and go out to play. At this time, you need to communicate more. Either let her accept this happily, or stay with her. Otherwise, if you come back from the trip happily, your girlfriend may be gone.

If she is happy to tell you not to worry about her, she hopes that you can play happily outside and not worry about her, but you cannot really ignore her at this time. When you have time, send more messages to let her know that you care about her.