What does my mom mean when she says. "Someday you'll do time for that young lady"?

When your mom says, "Someday you'll do time for that, young lady," she's likely using a figurative expression to indicate that your behavior or actions might have consequences in the future. It could suggest that she thinks you may face repercussions or "pay for" something you’ve done, whether it's a specific action or a general conduct. It's often said in a playful or teasing manner, but it can also indicate genuine concern about a behavior that she feels may lead to trouble later on. It's important to consider the context in which she said it to fully understand her intentions behind the comment.