Carrie has had a more successful career in the country music world, but Taylor Swift has been more successful overall on Top 40/Pop. Thing is both have traditional country songs on their albums, but their far from being traditional country, they're more mainstream country now. However Carrie has never said in interviews she's a traditional sounding singer, she said the great thing about country is you can have a balance of traditional country (Miranda), more pop-rockish country (Carrie) and crossover country (Taylor) in the same genre and they all make it the great genre it is.
If you want to talk about female artists who are bringing a traditional country sound then I suggest you listen to Jana Kramer's debut album, Miranda's Four the Record or Kellie's 100 Proof.