Easter egg: Go to the "special features" menu, then hover over the area just to the right of "Turn disc over". You'll see a circled "13" appear. Clicking on this takes you to the improvised "box of drugs" deleted scene.
Easter egg: The word Thirteen appears very briefly (a couple of seconds at most) as the main menu loads but is not clickable. However a video of the "Zen Chicken" can be accessed by disassembling the DVD to your PC. You can then save the video as a separate file.
Answer: Tracy acted like she had done everything Evie did before. She pretended she was already bad to become friends with them, so Evie thought she had found someone who was like her. Evie was definitely also in love with Tracy, but was also jealous since Tracy had a family who loved her. She wanted that. Yes she used Tracy, but she also cared about her.
I don't think Evie was romantically in love with Tracy. It was more about her wanting to *be* Tracy, with a mother like Tracy's. Also, she seemed to know that Tracy was only pretending to be "bad." I think Tracy's innocence made Evie sad, because there was a time when Evie was more like her.