I don't like either actress.
As far as the character of Rachel, I don't like her either.
Is it because I'm a woman?
She seems to lack all depth to me. In BB she was just "well I've got to do my job and be tough..." and that was it. You could never really understand why Bruce even liked her, other than the lame idea that just because he knew her as a kid, he'd fall in love with her later in life. Also there were no other female characters in this film besides her and it takes a far stronger character AND actress to balance that out.
Bottom line, if Rachel died in TDK (I seriously doubt it) I would cheer. Her character is useless except as a plot device. Her roll in the Batman franchise is to be tortured, bullied, pushed off rooftops, kidnapped, rescued, terrorized and messed with just to effect Bruce Wayne. It's so predictable. And if it keeps up in TDK (which from the trailer and spoilers it looks like it is) I will be very disappointed. It would be the 4th film Nolan made where something happening to the helpless woman motivated the central character(s). The only film he ever made where that didnt happen was Insomnia which was a remake of someone elses story! Give it up already. Not all women are helpless pawns in the games of men.