Personally, I think it is neither here nor there if someone did not attend the funeral. There is no rule about who should be there.
I have a good friend who did not attend a parent's funeral. Not out of disrespect, not out of a lack of love, but because that person could not handle the overwhelming grief and wanted to remember her parent only in life. She instead chose to go sit by the gravesite on many, many, many occasions after ..... talking to her deceased parent.
No, she isn't crazy, nor an ice addict. She was just a bereft person coping as best she could.
I'm sure some tongues probably wagged about her after the funeral. I didn't hear them, but it seems likely. But I think her lovely deceased parent would have supported her decision. And as her close friends, a group of us supported her decision too, once we were sure she was positive about it. In fact everyone close to her was fine with it, once they understood. And she has had no regrets.