I saw them; I definitely liked the final design best! I thought she looked kind of mean and/or angry in a lot of the early sketches, although I did like the one of her in pants. The blonde version looked just plain malicious. One change I especially liked is that they ended up giving her larger eyes than in the earlier versions, which I think looks really good on her. And, of course, there's the smile, too. She wouldn't be the Frankie I love without those eyes and that smile.
For those who missed it, here's the
Fosters Official Blog.