It may not be the sex talk, but it's still one of those awkward conversations. When your 3-year-old streaks naked around your guests, it's time to talk to her about modesty and private parts. While it's not a big deal to be naked as a toddler or baby, she's transitioning into an older child and needs to learn to cover up. You want to approach it just right, so she isn't embarrassed or ashamed about her body. So keep it simple and matter-of-fact. There really isn't anything to be embarrassed about.
Explain to your child where her private parts are. The easiest way to do that is to tell her that anything under her swimsuit is a private part.
Give the proper names for her private parts. Up until now, you might have been using nicknames like "pee pee" because the full names are too difficult for her to pronounce. By age 3, she should be able to say words such as breasts and vagina. Talk to her about these parts using a natural, relaxed voice. You might feel a bit uncomfortable but it's important that she doesn't.
Tell your daughter that her private parts are just for her. It is normal for her to be interested or curious about her body, but any exploration should be reserved for when she is in a private atmosphere. Give her examples of when it's OK to touch her private parts. This is usually in the bathroom or bedroom. Make sure she understands that she should come to you immediately if anyone asks to see or touch her private parts.