Should we have invited her?

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Two friends A and B are planning on going on a vacation trip. A persuaded my sister and I (who were also thinking about going somewhere) to join them. I don't know if I brought it up, or if it was my friend A, but we invited my best friend C, who is also a very close friend of A. C tells our best friend D about our plan to go on vacation, and she said she is also going on a trip with her family. So we (A, B, C, my sister and I) all went on a trip together, and got back a few weeks ago. Now D texts me that she's upset that we didn't tell her we were going...