Right,that's her...
In my opinion, Kristen Stewart looks like the regular girl next-door, which is good because that's how Bella is supposed to look.
Renesmee,on the other hand,is decribed as the prettiest child even been,so it's normal that the actress is small,cute and beautiful.
I believe Mackenzie Foy is a good choice,I believe she can portray Renesmee.
I heard that in Breaking Dawn 2, there are going to be used some really high technologies to the actress,just like the ones used in 'Benjamin Button' because Renesmee grows incredibly fast.
I think Breaking Dawn is going to be awesome!!!(: [Actually,I can't wait for: 1) the vampire gathering 2) the part when Jacob imprints on Renesmee]