I ghosted my best friend for six years.
For six years? Why would you ghost your best friend for so long?
I was being selfish and wasn't thankful for her help.
You need to call your friend and apologize for your behavior. It is wrong to ignore your friend because of your own selfishness.
I won't apologize, she can wait until I have time for her, I have things to do.
Ghosting people is wrong, but doing it to your best friend is especially unkind. There are reasons you might have for avoiding her, but it's time to step up and apologize for going silent.