Is AUTHOR wrong in the post ? POST : Obligatory first time poster warning and trigger warning for self harm and depression.

My friend has depression. We're both teenagers and have been at the same school years. 

A few years ago we were best friends and with a stroke of luck, we were finally in the same class! At the start of the year, she tells me a secret that she says I'm not allowed to tell anyone, ever. She's cutting, and she told me this over text. I was 12 and very confused and frightened, but viewed her as my best friend so I just told her that she had my full support and I would help her. 

We never mention it, until about 3 months later, when she texts me again about this. This time she included a picture and since it was through instagram dm's, I had no idea what it was until I opened it. The photo was of her stomach with awful red lines, blood and scars on it. Again, I told her that she was my friend, and I would look after her. But inside I just felt awful. I wanted to tell someone, but back then I was so young and a secret is a secret! Snitches get stitches! I told her to stop cutting, but she wouldn't listen. 

Over the next few months she kept telling me about her depression, anxiety, insomnia and continual self harming. Occasionally she would send a photo. We never talked about it in person, but every night she would just text and text. She was in an awful part of her life which she needed to get out of. But the things she were saying were also freaking me out and the photos made my skin crawl. Sometimes I wouldn't sleep because I was so worried that she would kill herself so instead I texted her to make sure she was still replying. There was one time she didn't reply for 2 hours and I thought she had done it so I frantically texted her brother to check up on her. She had simply started ignoring my texts and instead texting this boy that she had met. I was relieved that she was alive but utterly pissed as I'd spent the last hour contemplating whether or not to call the cops. 

I don't know what she felt, but I felt used and like a garbage dump, just for her to unload her insecurities onto before moving on. 

The final straw was when she sent photos of her self harm to another guy that she had met through mutual friends. This guy was 16 when we were 13, and went to a completely different school. She had sent them because he told her to fuck off when she continuously texted him at night. This wasn't her first rodeo in chatting with random guys online, but this time she had not only given him her instagram and phone number, but also mine! I guess he didn't appreciate the unsolicited bloodied photos(that were of her in her underwear too), because then in the most awful act of 'revenge' he sent the photos on a massive group chat he created with her, me, and about 10 of her other friends. He also sent screenshots of their texts which is how I learnt what she had done. Afterwards I begged him to delete the photos off of his phone on behalf of her.

After more than half a year of this, I couldn't stand this anymore. One morning I told our teacher and I couldn't stop crying. If my face were China, then my tears from the left eye could've been the Yellow River and the right the Yangtze. Thankfully, the teacher was fantastic and understanding. She sent me to the school psychologist before calling *her* up. Now if my face tears were like rivers, hers was the entire fucking ocean. She was a human faucet. I got called back to the teacher's office, where Miss Amazon River started hugging me and asking if we were still friends. She explained that since we were best friends, I should listen to her and she would do the same. I said something the lines of "Yeah, friends..." and she took it to heart. But I couldn't even look at her without wanting to bawl like a complete baby again.

After that I stopped hanging out with her and make stupid excuses every time she wants to call me. When she texts I just reply with something small. 

Am I the asshole for only being able to see her for the depression and self harm instead of her true self? Am I the asshole for not being her best friend anymore? Is it selfish? 

I know that she's on antidepressants now, but I don't know if she's stopped self harming. I hope she's doing well, but we don't really talk anymore.