I second what MadB said about mother's knowing if something isn't quite right. You're not being ridiculous, just concerned for your DD.
I'd say ask your maternal health nurse or GP (or both) about it and see what they say. I know that it's too early to diagnose for something on the Austism spectrum, as a few of the criteria relate to social and language skills etc. Still, if you're worried, I'd be asking for advice.