Sorry to hear that, i know how sad it feels. I've been in that situation as well several times. I had someone, we've been best friend (at least that's what i thought) for years since 7th grade. We experienced similar family issue so we absolutely understand and trust each other. We barely had fight or such but then after graduated from high school we started to drifting apart. Unlike before, she barely contacted me. After that I was always the one who started the conversations, i just wanted to say hello and how well everything is going on once in a while but she often responded with cold manner or even just read the message without a reply. She stopped talking without a reason.
Unlike me, she's not an introvert type so i realized that maybe she got better friends than me. So i eventually stopped to text or chat her first to see if she even realize we haven't talked but she didn't. I just stuck silently missing her knowing it's not worth anymore because she obviously no longer care, i felt like "sorry to bother you with my friendship".
Anyway, I heard a quote saying "A good friend is worth pursuing for" but why would a good friend running away??