There have been three not two. She was the little girl in the spacesuit before she was Rory and Amy's friend that grew up with them and then regenerated into the one we now have. This will be the last one.

The rest of you haters should pray you would age as gracefully as Ms. Kingston. She looks amazing today just as she always has, since her ER days and before. She is truly fantastic and I wouldn't care if she were 90 there can only be one River Song.