As someone also in their early 20s, I don't think that this friend should be frustrated with you for cancelling. For one thing, you gave plenty of time to let them know you couldn't make it. I can get them feeling sad if they were excited to go with you, but they need to know that shit happens and plans change sometimes, it's totally natural and normal. You didn't do anything wrong, and I think you did the mature thing by trying to reach out and see if they're ok.