Wow, great job! Super concept. Creepy art, creepy music. That "dark carnival" motif keeps everything disturbingly off-kilter. I actually enjoyed the character animations and the models. Twisted.
I didn't have much trouble figuring out that the sisters could split and then rejoin, but you might want to add that into the tutorial. The mechanics here are actually a bit complex.
I was surprised that the puzzles never became super tough, but it is a short-term project. My only real complaints are that the pessimistic sister moves too slow, even though it fits her character, and that the game eventually becomes tedious. Part of that is because of the inability to jump or walk off ledges, causing the characters to have to walk up and down ladders repeatedly, but I understand that its part of the gameplay (jumps and edge-falling would make the game meaningless). It ends fast enough that it never really becomes an issue.
In the previous reviews, there's some dissatisfaction with the ending, but I think I get it. You're saying, "And the story went on and on, and the show went on and on... and only one thing could end it."
This would be a great full game. I wonder if there's some variations you could add to keep it interesting after 4 or 5 levels?