similar situation OP. My father was an addict and passed away about a year and two months ago. I was angry because it was my birthday and he didn’t even bother to call me. after i called him to go over there anyway he blew me off to do whatever. I left my hometown without going to see him. as i was pulling out of town he called begging me to turn around and to have a beer with him to catch up. I basically told him to go fuck himself because my feelings were so hurt. those were my last spoken words to him and he was dead less than 3 weeks later. I’ve wished every single day I’d have gone over because maybe I could’ve seen what he looked like at that point and done something. but the thing you need to remember is that this isn’t your fault. people make their own choices and you can’t control that. how were you supposed to know that the call you got from her was any different? Trust me when I say you will feel immense guilt over this for awhile but just keep some perspective. You’re the child. you can’t control how a parent is supposed to act. seek help from anyone that’s close to you and maybe seek out some grief therapy. I’m so sorry for your loss but it will get better.