Her set of rejection letters can be entertaining, after one has gotten over the initial disappointment of failing to sell. It's more honest. First, this is a buyers' market. Every editor gets far more stories than he or she could possibly use, even if every one was a jewel. So luck and timing play a pretty big role in getting published.
Editors try to balance a magazine, so that the stories complement each other.
As the writer has no idea what the editor has in inventory, this part of marketing short fiction is a gamble. Some stories are rejected because they are not very good. My own first stories were not very good and some of the ones I'm writing now are probably not very good. Obviously, I think they are good or I wouldn't write them. Sometimes it takes a rejection for me to realize that the story needs revision.