I'm really hoping this "friend" of yours is more of a friend the other days of the year then. If not, they are not a friend worth keeping. And I hope there were other friends on your party who actually cared. Non the less, Happy birthday!

I'd say they haven't been a friend for about 8 years

Happy birthday!?

If she "forgot" your birthday party for 8 years in a row, she's not your best friend, she's not even a friend. Drop her and find someone worth being friends with

is that just how they are, or do they just flake on you?

I have to have reminders set up for my friends'- and my own!- birthday, because I just can't remember them otherwise. That said, that was something I resolved to do because I wanted to make sure to remember and tell them happy birthday, even if they don't hugely celebrate it. Maybe you should ask your friend about it...? Or "forget" their's of you haven't already.

"Best friend"

and ur still friends with this person. no one deserves to be treated like that and u should find a new friend

i mean idk if i would even consider that person a best friend or friend

Doesn't sound like a best friend to me