The star told Flicks and Bits that she has most enjoyed portraying the vampire's sensitive side.
"The beauty of being an artist is that we all have regrets about performances at different points in time," Reed explained. "You have to just remember that, that is a photograph in time and you have to walk away from whatever you did, move on and appreciate that performance - sort of isolate it."
Reed continued: "One of the most challenging things about playing Rosalie has been knowing personally who she is and all that she's capable of, where she's coming from. And Stephenie Meyer, she really wrote some multi-faceted, multi-dynamic characters.
"There's so much depth to all of them. So there's definitely been some frustrations along the way I feel, in not being able to explore all sides of who you're playing - almost feeling defensive of your character. I'm really happy that we made it to the place we did, I'm really happy I got to show a more vulnerable and sensitive side to Rosalie."
The star concluded: "I found it really fascinating to watch how the fans closely associate you with whoever you're playing, it's very subconscious. Now being on the side of the protagonist, I think the fans are accepting me even more, that's been great."
Reed previously said that the end of The Twilight Saga has been "overwhelming".
"I love these movies and I love my character, I love my fans and the cast and all the directors," she said in October.
The Twilight Saga: Breaking Dawn - Part 2 is now playing in cinemas. Watch a trailer below:
Breaking Dawn - Part 2 UK premiere in pictures:
Copyright: PA Images Dominic Lipinski/PA Wire