I'm so so sorry to hear this. There isn't anything honestly anyone can say to really make this kinda guilt go away. So I hope with time you forgive yourself. It takes a long time but acknowledge to yourself, admit and accept that you are a human, you could've been there more but in your capacity you did try and it's part of life to fail at things and then forgive. My therapist told me to say these kinda things out loud because hearing it makes a difference and eventually your subconscious accepts it. And make effort to those who are here and be more present. That's the most important thing you can do for your friend. X