I had similar things happen with my three daughters in their high school softball team, but not to the national degree of your niece.
Their high school coach never submitted any names for recognition. From what I was told, the coach needs to be a member of some coaches group to which she never joined. In any event, one of my daughters hit just under .600, switch hit, had somewhere around 4-5 home runs, etc. She also excelled against top competition outside of the conference. She was all conference and even recognized in a local paper for an all suburban team. No votes for all region, or even all state. The girls were frustrated at first, but by the time my third daughter came along, she didn't expect much of anything outside of all conference. My oldest daughter went to play softball in college. The other two decided to focus on school. All three earned multiple unanimous all-conference honors.
I hope things turn out well for your niece. It sounds like she will be in good standing.