Tongue - in - Cheek(not serious)
Why were you teasing Sonia about her new hairdo? She really took offense at what you said.
I didn't mean to offend her. I was simply making a tongue-in-cheek remark when I said that it was too elaborate for a girl of her young, tender age.
Well, She thought you were serious. She had no idea that you were just saying that as a joke.
I'm really sorry. I suppose I owe her an apology.
take offense at = ~に立腹する
tongue-in-cheek = からかい半分の
remark = 発言
elaborate = 凝った、手のこんだ (labor)