Jewish jellies: what would a rabbi say in this situation?

A friend of mine, we’ll call her Carol, has a funeral service to attend on Yum Kippur. The son of a friend died. Not a very close friend, but still close enough that usually Carol would go. Carol told me too bad her friend didn’t think about it being Yum Kippur before she planned it, because Carol won’t be able to go because of the holiday. I told Carol, “just go. It’s just a couple hours. God will understand.” She replied to me, it isn’t God understanding, it’s about me and how I will feel.” She went on a little more about Yum Kippur being a day of atonement and her thoughts and focus should be on that, and she fasts. Well, I know what the day is, I just think she should still go to the funeral. This is a funeral of someone’s child dying before them. It is an adult child, but still.

So what would the Rabbis say? I was raised in a non-religious home, so I don’t have any personal experience when these types of decisions had to be made.

Carol is reformed, she does take the holidays very seriously though, and she believes in God.

I support whatever she decides, she said she is still thinking about it. She said she might ask a Rabbi. She doesn’t belong to a synagogue, not that it matters.