Hi Helen,
My N mom never used *sarcastic* baby talk, but did use regular baby talk all her life. When we were in our 30s and 40s, she would continue to use baby talk as part of normal conversation. For example, going to the bathroom was "making a poo poo," and so on. I always figured that it was one more way to try and force us to remain children. After my sister, brother, and I grew up, we were never treated as adults.
I was the eldest of her three children, and my NM started wigging out on me when I became a teenager. She was completely unable to handle the loss of control . . . a child growing up and developing independent thoughts. She tried to keep me a child, sheltering me from things teenagers did, cutting my hair in a childlike style, buying clothes that looked like they were designed for a young child. I always felt that the continued baby talk was another form of control, and part of her refusal to acknowledge that the child who was never supposed to grow up, did.
Kathy