The show writers might not have cared about that. They didn't seem to get the concept of friendship. I don't think anyone was ever a true friend to anyone on the show.
They all were frenemies or just plain forgotten.
Though Mercedes and Quinn were who I thought of first while making that post.
She let Quinn stay at her house and they seemed like they were growing close and then nothing. And so many other where a character might show a little support or whatever and then nothing.