If she is imitating sexual acts, she could have seen them on the Internet. You noted that she has access to an iPad. That’s one possibility.
She could have seen them on television, even in a suggestive commercial. That’s a possibility.
All other possibilities should be considered, including sexual abuse. Statistically speaking, most sexual abuse of children is committed by someone the child knows. It’s rarely a stranger. Try to think about the people with whom your child interacts.
You seem to be getting secondhand information from the nanny. Have you observed these behaviors yourself? If not, you should. You could put a video recorder in your home. They are relatively cheap. You can get a high quality IP camera for about $100. That way you can clarify what is meant by “do[ing] sexual acts including touching her abdomen.” Touching one’s abdomen is not necessarily a sexual act. Once you observe the behavior, you might have a better idea about what is happening.
You can also ask your daughter directly about the behavior. You should talk to a therapist about how to formulate your questions.
If you have not questioned your daughter and you have not personally observed the behavior, then you still have more information to gather. Once you gather more information, contact a local mental health professional who specializes in working with children. Provide them with all of the details and ask for their advice. They can provide you with specific instructions about how to proceed. Please take care.
Dr. Kristina Randle