Child-like devotion doesn't mean functioning in a silly or cute way like a child. It means always turning to our Lady(prayer, petition, discernment, and imitation) in all things, as a child is wholly dependent on their parents. We "fly unto thee, o virgin of virgins". That is what it means.
St. Paul answers your question about whether adults should act as adults(responsible). And, the answer is, you should act as an adult. "When I was a child, I spoke as a child, I understood as a child, I thought as a child. But, when I became a man(adult), I put away the things of a child." - 1 corinthians 13-11
I suspect by your concern, that you are perhaps making a mistake or bordering on making a mistake in your devotion.
Also, if you are vocalizing your "talking to her throughout the day", do stop that. That is protestant and irreverent. Prayer(the lifting of ones heart and mind to God, and even to our Lady) must be reverent. This is why we bow our head at the name of the Lord(whether in prayer or daily speech).