Well, for starters there's the fact that the taxi was found miles away from her destination, so we don't actually know she was coherent enough to do that. 

Plus, she was found unconscious at the time the taxi was found.  She obviously passed out at some point - that's not at issue (are you suggesting it is?). The issue is whether she passed out before or after her clothing was removed. 

And this is to say nothing of the fact that this cab driver had several previous complaints about sexual misconduct from female passengers. See the writeup of this case on CBC - there's a lot of useful background.