Thanks. It doesn't sound really unusual, and as one person suggested, we might have said something about it. It's just that DD9 was there and her memory is pretty flawless...
But anyway, thanks for the Starfall recommendaiton. The one reading game that DD4 does play is Clifford Phonics (old but great, BTW) so she might just be absorbing this stuff through that and cartoons. With DD9 we went through a reading course very deliberately.
Another poster pointed out that self-consciousness could have a lot to do with it, and DD4 is extremely sensitive and actually our "difficult child"...I would not be surprised if she ends up surprising us if the stats on IQ ranges and siblings are correct.