How do I let people go??

I’ve been having this problem/feeling lately. I was best friend with this girl for 13 years. I’m going to call her “L”. L and I met in kindergarten and were best friend’s since then. We did almost everything together. Her parents would take me with them everywhere they went because L was an only kid. I was at L’s house everyday and it was like my second home. We made a lot of amazing and fun memories together. I was always there for L. I went with them to go out ine of their dogs down and was there when her grandma past away. I was always her shoulder to cry on and she was mine. We were in a big friend group and we were all very close. Sophomore year, a guy in our friend group started dating a girl and she is very toxic. She always had to be the center of attention and would cry when she didn’t get her way. We didn’t like being around her all that much cause she would start whining. One day, L went on vacation so the annoying girl, another friend of ours, and I had to watch their dogs. I was there every single day with the dogs. The annoying one was almost never there because she would rather be with her boyfriend and his friends and the the other friend was always busy. I barely ever had time to go out and have fun. One night my boyfriend and his friend invited me to a fair. I got a little tipsy and woke up an hour late to go feed the dogs. I rushed over there after realizing. I got a text from the other friend and she said she already fed them. I also forgot to mention the annoying one said she would do the dishes because she loved doing it. The next day L go home from her trip. I woke up to a huge paragraph from her calling me an irresponsible person and I saying I have no respect for her house. I was so confused. Apparently, I left her house a huge mess with a sink full of dishes and she was told I didn’t feed her dogs. After that day, we barely ever talked again. It’s been a year and we still haven’t talked. I am heart broken by this and tried talking to her to make things better but she would ignore me. I still can’t seem to get my head around it all and see that she is actually gone. I loved her and her family so much. I don’t know how to let it all go.