Hey Tan

I'm a Speechie. To me, it sounds like Izzy is putting all her efforts into developing her motor skills (which sound fantastic!)...

I wouldn't worry to much about the chattering...keep an eye on it, for sure, but don't stress about it.

Developmental milestones are important...but they shouldn't be so narrow that it doesn't allow for individuality. They are approximations of when things should happen...and they are AVERAGES not exacts.

Keep on doing what you are doing...talking to her...repeating sounds, having fun with language (rhyming, making silly sounds, etc.). Keep reading to her...and it will all come together.