I don't really like blaming any one person for things. I think perhaps everyone in the storyline didn't make the best decisions at one point in time or another.
Still, they did what they thought was best at the time. Juliet was only a teenager, wasn't she? I think she acted quite maturely for her age.
they were both teens. romeo was 16 and juliet was 13. regardless, she acted dead and he killed himself with poison, then she took his knife (as she couldn't li.ck poison off his lips because he drank it all) and she stabbed herself. However, their parents were the ones in dispute, but as adults tend to do that, romeo, I believe was simply tempted by taboo, ergo, I think it's the parents's fault for being in dispute which lead the two to meeting, but for the tragedy, it's all juliet. If she hadn't have faked her death, romeo wouldn't have commited suicide. And, if I'm not mistaken, he KILLED her arranged husband. sooooooooooo
they were both at fault