Girl who I friendzoned treats me like we are in a relationship?

I'll try to make this as quick as possible. Basically my female friend a while ago admitted to me that she had feelings for me. At the time I was a little torn about this, but I came to the conclusion that I didn't really feel the same way about her and that we would be better off as friends. I told her this clearly and whilst she was upset (and I felt really bad because I didn't want to hurt her feelings), she accepted that we could still be friends. However, it didn't take long for me to realise that she wasn't really adhering to what we agreed to. If we're out together (not always just us, sometimes in a group) and another girl shows some interest/flirts, my friend puts herself between us and tries to divert the attention away. I don't particularly mind it in these situations, because usually I'm not that interested in the other girl. She also gets upset if I don't text her goodnight and good morning every night and morning (I thought that's somewhat childish given that we are not in a relationship and we're both 20). I did tell her a few months ago that she can't treat me like I'm her boyfriend and she seemingly did accept it at the time and things seemed to be going smoothly but recently she slipped into the possessive behaviour again, hence why I'm making this post. Like I said, it is annoying but didn't really make me super worried when it came to speaking to other girls, since I wasn't usually interested in them. However, there is now a girl that I am interested in and would like to get to know better, but I am worried that my friend will not take this well at all, and potentially ruin any chances I have.
Despite everything I've said; I haven't dropped her as a friend as she has been really good to me, and been there for me. Personally it just feels wrong to drop a friend just because they like you a lot. I like her as a friend, and I enjoy talking to her as a friend, but I don't want anything more with her.

Thanks in advance for the responses.
Girl who I friendzoned treats me like we are in a relationship?
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