I watched the entire series for the first time in February, and rewatched some episodes several times since. At no time did Blalock's performance
ring false for me. There were things the scripts had her do that didn't seem right to me sometimes, but I can't blame that on her interpretation of the character.
Unfortunately modern television often takes actors with little actual performing experience (or none at all) and gives them their own show. Reality shows are the worst case scenario example, yet somehow these non-entities become famous "stars".