Translate this joke, where is the joke?

My friend Nancy and I decided to let her old mother know the magic of the Internet. First, we went to Ask Jeeves website (similar to Baidu Know, Q&A) and told her that this website could answer any questions she raised.

Nancy's mother was suspicious until Nancy said, "It's true, Mom. Think of a problem. " When I was sitting in front of the computer with my fingers on the keyboard ready to type, she thought for a moment and said, "What do you think of Helen menstruation?"

For example, if you tell your family that Baidu knows you can ask questions, she said, then ask your aunt for me.

I don't know if I understand this.