Did I handle this situation with my platonic female friend of mine correctly?

Okay so I had this very good female friend who I was very close with. I do not have any romantic interest in her buy I care about her very much as a friend and she would always confide in me and we would both encourage each other. She has a very jealous boyfriend and she is a jealous girlfriend with him as well. They both hate it when the other has friends or talks, texts, hang out with a member of the opposite sex. However, me and her were good friends and she trusted me. She would always talk to me about her problems with her boyfriend and I would always try to help her and give her advice. I was always very supportive of her relationship with her boyfriend and tried to help her, like a true, good friend should. Me and her used to work together but then I left the job. However, we both joined a technical college course together and we were excited to be doing it together as friends. She even encouraged me to do it with her. So we hung out together and talked all the time at school. Everything was good. However, all of a sudden she started distancing herself and acting more cold with me. I never did anything inappropriate, flirtatious, or wrong to her. However, she told me she started thinking that I like her as more than friends for no apparent reason. She stated that it was because when we walk together in the halls and during the breaks I wait outside the restroom for her. Even though we had been doing that for several months at this point and she understood why I did it before as we would always hang out together us 2. I assured her that I did not like her in that way and she said she believed me and trusted me. However, things remained a little bit weird. She blocked me on messenger after I sent her a happy thanksgiving text message in a platonic sense as I do with my other close female friends. I reassured her that she has nothing to worry about and she told me that she knows that but that I have annoyed her. Me and her used to always enjoy texting each other before and did not have a problem with it before. I tool it easy for a couple of weeks but I still tried to assure her that I have done nothing wrong however, she told me that she truly does believe me in what I'm saying to her but at the same time she feels it is disrespectful to her boyfriend for us to be so close and that she would not like for him to have a female friend as good as me either so she doesn't want to feel like she is doing something wrong to her boyfriend. I asked if we could take a selfie together as friends but she said no. We went on winter break and did not have contact with each other. She took me off her snapchat and when I asked her about it she told me that she took off all of the guy friends from her snapchat. I wrote a letter to her reassuring to her that she can trust me, apologized for any misunderstanding, letting her know that I care about her as a friend and I gave it to her on the last day of the program. She told me she would read it later as we would be busy in clinicals that day. Before she left I told her God bless you and she said the same to me. I just feel like she handled the whole situation so poorly because I would honestly never do anything to hurt her. I acted in good faith. She told me that her boyfriend gets very angry with her when it comes to her speaking with other guys at all. Did I handle this correctly? I understand if she wants to respect her boyfriend but their is a better, more communication oriented way to handle this.