Friendship downgraded.

Hi. I have been friends for around 8 years with a lovely person. Over the past 18 months or so we have become best friends and even suggested we would be soulmates at one point. We have supported each other through some very difficult times, she supporting me as much as i her. In the Spring she lost a dog and having gone through a difficult time with relationships this dog meant alot to her. So when it died i kept messaging her to make sure she was ok and she told me after this had saved her life. I was then diagnosed with codependency and she supported me through that. A few months ago she rang me as she had a fall out with her partner having put weight on due to drinking. She rang me at 11.30 at night and i stayed on the phone for an hour and a half and again she said i had saved her that night by not judging her and just listening and supporting. She said no matter how hard i tried i would never get rid of her and that she would love me forever. All seemed well. We did not want anything more than what we had for we had other people in our lives but we did agree we had a very special, if platonic relationship.

The only thing i do challenge her with is i get anxiety because i lost a younger brother many years ago i worry about people close to me and worry i would lose them so every now and then, once a month maybe, i would just ask if everything was ok but my friend also understood that and allowed it to happen.

Now a couple of months ago she had a few more issues with her eldest son who was in trouble with the police and we planned a walk. I asked her if we were ok and she told me she could not cope with it anymore. She blocked me, just out of the blue. Two weeks later when we talked there was no, sorry, or any such thing, she told me the following

That i dominated and was too persistant.(We did text each other most days so it was two sided)
That i thought i was helping when really i was stroking my own ego and making myself feel better. (I only ever supported her as a friend should do)
That she could not talk to me to protect herself and her family (as if i had committed some mortal sin - if i have she will not tell me what this is supposed to be)

It feels like i have been stabbed in the back, like a betrayal. All my support was out of love, and because i care and now she has attacked me for a reason that she won't discuss and has downgraded me from best friend to just friend, and not even on the media we used (whatsapp) and told me that we cant talk like we used to as it is not appropriate.

To say i am heartbroken. She clearly has something in her head that i have done that is really wrong but i know i haven't done anything at all, just supported and i am struggling to wrap my head around it.

What do i do? Help? I am devestated to lose such a great best friend.