fantasy or reality.
I guess it comes down to one of two things - we have a reliable narrator, or an unreliable narrator.
there are various points that support both viewpoints. If she is reliable, even if we believe that she is "making the story up" we know that Homer does exist because she searched him on the internet and found him. This is partly supported by the fact that she has knowledge of the unknowable. She knows that Hap had a teacher who inspired him to follow the path that he took, and how Hap had killed him, when it is clear that Hap did not tell her this. She may have drawn her own conclusions, but because she is narrating the story to the group, she does have knowledge that she should not have.
If she is unreliable as a narrator then we cannot trust anything that she has told anyone. She may have lied to herself about seeing the video of Homer.
If she is a completely reliable narrator, then everything she said is true, they are angels, and she had knowledge of the unknowable possibly because of her repeated NDE.
So, what's my take on this? I suspect that she has some sort of powers that were tapped into as a result of the NDE and that Hap's experiments were accurate/truthful. I think that she understood the powers differently than what was probably happening, that she was able to travel between dimensions and also project her consciousness on our own physical plane. I think that the revelation that what she heard in her one NDE - the sound of the rings of saturn - was not some sort of accident or throw away line in the show. I'm not entirely sure where it's all going, but if there is a continuation of the series it certainly cant end with "sorry, everything was just made up"