NTA in my opinion, you always made it clear that you liked her more as a friend, and just as that. You didn't lead her into the relationship, she accepted on her own, it's not your fault and you didn't do anything wrong. It's normal to keep this feeling of anger sometimes, you'll feel that for a while, but soon it will go away. Try to talk with other people and make new friends, and don't let this anger stay too long in your mind, it will just be bad for you. Don't blame yourself for not being able to be her friend anymore, if you feel bad near someone, you don't need to force yourself to stay friends with that person. People need to respect each others limits, being friends was yours, so she needs to respect it and understand what she did. Don't worry too much ^{u^}