Sorry for your loss x.
When my father passed away my besties did not attend the funeral, they had their own things going on and I understand and respect that. Sure it would have been nice to have them there but it wasnt the end of the world. I didn't think they were being rude and I wasn't offended.
They still provide me with a mountain of support and give me a shoulder to cry on to this day, that means more to me than attending the funeral.