I don't think you bear any blame here. You did nothing wrong except keep an open heart. She used you for a place to stay. She probably already knew that you had feelings for her and she played those too but added the "platonic" tag to make it seem okay. I'll guarantee the boyfriend didn't know she slept in your bed or else he would have kicked your behind long ago.
If a girl is going to sleep in your bed, then you have every right to expect that she will want more. You should have made her sleep on the couch and not with you. If she was kissing you on the lips then she was either giving you a go signal or playing you again.
If she was a true friend, she would have talked to you about this later to clear things up. Good friends do not let their close relationships get away. If they really love you, they will fix it. Her parents knew what she was doing and they know her best. Listen to them.
Don't think you lost the perfect friendship, there was nothing perfect about that. Be glad that you are out of it and be open to meeting someone new. Don't let her call the shots anymore, if she doesn't want to talk to you then let her go. It's good to know your feelings are changing. Sorry this happened to you.
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No matter what your age, you don't need to change the world to find love, sometimes all that has to change is you. Be open to the possibilities.