Hey there, Ive had a similar experience! Except the sudden cold shoulder was coming from me! When I first started dating, I had issues with self-sabotage. As soon as things would start to get "real", I shut down. Ghosting, nitpicking, anxiety-induced negativity; I regret it. I was working through trauma and putting up lots of walls, while trying to untangle my own feelings. Of course, she may be acting this way for totally different reasons, but I felt compelled to share. If shes having the same problems as I am, she may just need some space to work it out. I dont think you did anything wrong, and I think its healthy that you read the signs she was giving you. I had to work extrememly hard to break these toxic habits, and my partner is patient and compassionate, she has helped me grow immensely. :) If you are really into her, she may be more receptive to a relationship without the pressure of being a couple; a supportive friend may be all shes able to reciprocate at this time. Remember to take care of yourself and your needs, and dont be afraid to speak your mind.
Best of luck friend