Friendship break up

Hi everyone. I am new in this community and I want to share something I am going through. I have had this friendship for the past 20 years. The last few months I was in crisis and relied heavily on my friend. Upon looking back I found there were 6-7 emails that were very emotional that were probably very hard for anyone to navigate. It was a huge relief for me just having someone to vent to. I thought we had a relationship that I can rely upon. Everything was going fine when she tried to call me twice which I rejected. I am very awkward at phone conversations so I was admittedly reluctant. Despite that, I did give a few time slots that would work for me. After that she texted me and said she is disappointed that I am not willing to answer her calls. She said I am not putting enough effort so she would not put effort into answering my messages as it is emotionally draining. She will also stop putting effort into the emotionally draining friendship. This was the final straw for me. I was hurt and angry. I pondered over it for a few days and finally sent an email ending the friendship. Now I am feeling a bit guilty and wondering if I was rash. From her perspective I took advantage of her by overly venting and when she voiced concerns I cut off the friendship. But there were many aspects of the relationship that wasn’t working. She has the tendency to take off and leave and drop in at whim. She is very secretive and unwilling to trust me with any information like she does with our other mutual friends. Spending time with her has not been fun in a long while. Even when she does shows up I feel she is not fully there. She seems to be having more fun when we are with other friends. When it is just the both of us she doesn’t seem happy. So there are many reasons why I feel this friendship was more like a zombie. I think I did make the right decision but maybe I was a bit harsh in the way I ended it. I just wanted to share it here. I would welcome any perspective. Thanks for reading.