Honestly I thought she was a miscast because she looked younger than Hayden in AotC when I knew Padme was going to be Anakin's wife. As for the acting, her performance was not impressive in TPM while the character's lines aren't impressive. AotC is probably Padme's best one, she did those politician scenes fine but there is no chemistry between the couple. I believe that's mostly Lucas' fault because of his directing and script. RotS focused on Anakin mostly, so Padme's role was simply "Anakin's wife", she showed struggle between love and her political faith while the scenes she got was not enough. I think Lucas is responsible for Padme's character not being impressive, to be fair Leia's character wasn't better, there was no struggle in her character, she was totally kept away from the conflict of "Vader and his children". However, I don't understand why so many people blame Hayden when Natilie's character and performance was worse.