It's been 6 years since I've lost my best friend

I know most of you probably don't care and that's ok. Simply press the downvote button and move on. I've been keeping this inside for way too long and I feel like I really have to vent it out this year, so keep on reading, if you don't mind.
November 2011, at the age of 16, my best friend got hit by a drunk driver on her way home from school, never made it to the hospital. It was my first encounter with this kind of emotions and it hit me like a train (I cried for months). We knew each other for 4 year prior that, she was the first person to ever reach out to me. Brilliant, beautiful coder girl and simply the most gentle person I've ever known. She introduced me to coding (I used to like programming only). And just like that, suddenly gone. I didn't even attend to her funeral, never again have I seen her parents. Never seen the picture of her on her tombstone, never visited her grave.
The first year without her was rough, and I decided to do something really nice for other people the day of her birthday and have been doing it ever since (probably the only day in the year that I'm ever nice to other people), but it never got any easier, as I often told myself that she's watching over me.
Last week I've been invited to help with the cleaning duty by her brother and I, for some reason, agreed. Things are about to get real again really soon and I'm terrified more than I have ever been in my life.

Anyway, thanks for listening (I'll probably delete this later) and good night, imgur.