I don't like my bestfriend now

She decided to leave me to focus on herself yesterday (she sent me a paragraph why), i have abandonment issues so that's why it left me paranoid, she probably thinks it's so easy for me to move on, I struggle to move on because of the harm she did to me, we had a healthy friendship before all this, she has made me overthink,I thought she cared for me but she left me in the end, I know nothing lasts forever, but she literally promised multiple times she wouldn't leave me when I was at my lowest weeks ago, now she left me at my lowest yesterday without even giving me a chance to reply, I am incredibly frustrated by what she did, she caused me harm, and I thought she was there for me even until the end, and I also had worried that she will eventually leave me weeks ago and it just became true, I can't stop thinking about it since yesterday I saw it.