You're referencing the classic Southern American English phrase "She's the dozen(s) of", also known as "She's the mother of" or simply "Mama".

In this context, when someone says "She's the dozens of", they're not referring to a large quantity (like 12), but rather indicating that the person being spoken about is the mother. It's a colloquial expression used to show respect and affection.

Example: "She's the dozens of, she's always taking care of us."