All three examples sound correct to me. You could even say
Du siehst heute wie ein Mädchen aus.
However you would usually try to keep the connection as close as possible. So the first and second example are "better" than the third or mine above.
It might get hard to get the context if the sentence gets longer. For example:
Ich füllte das Formular schneller als mein Mitschüler, dessen Stift leider nicht funktionierte, weil er vergessen hatte, eine Ersatztintenpatrone einzupacken, aus.
(I filled in the form faster as my class mate, who's pen didn't work as he had forgotten to bring replacement ink)
While correct, this would give the reader - even a German - a hard time :-)