Can I please have some help finding out what book this is?! It's driving me crazy!!!?

There was this book I found once in Borders, It had a dark blue rectangular pendant attached to a necklace on the cover an the background was black. The book was about a teenage girl who's friend died mysteriously and while she's at the funeral, she sees this teenage boy dressed in black who seemed to know the girls friend who died and was standing out in the rain and bowed his head as if in respect when the "dead" girls best friend looked at him. It turns out later that the girl didn't die, but she was keeping a secret and the boy in black at the funeral was in on it. Apparently a whole love triangle forms between the best-friend, the boy in black and another boy... PLEASE HELP!!!!! don't answer if you don't know!!!!! Thanks!!!
If you can't help, but you might have an idea or any kind of info on this story, I am extremely grateful for it. So all of you who can help me, Thank you so, so much! I am extremely grateful for any information you may have!