Am I overthinking this? How do I interpret this?

I am arranging to meet one of my friends this weekend. I had a specific day in the diary (this Sunday) arranged with her for about three weeks now.

She has just got back to me asking if I am still okay for Sunday, but also did I mind if her other friend (they are very close) joins us too. She says that her other friend is coming to visit her this weekend, as it is the only one she is free before Christmas. My friend did say 'if you'd rather do another time no worries'. What does 'no worries' mean in this context?

Do you think that this is a sign that my friend was too nervous to meet me on her own, or am I overthinking it?