Silence in the car

When we drive home from preschool, Janey never talks. We are all talkers except her. We drove cross country last summer and there was barely a moment without talking. So it's hard, that 20 minutes without a word from her. I chat away to fill the silence. The other day I was tired of it, and just stayed silent too. She didn't notice or care, in fact, she seemed happy about it. I stayed mostly quiet at home, and she played in the driveway for a long time, seeming to be happy I wasn't bugging her with a lot of questions. She says her little things now and then, but if I don't talk, mostly, she doesn't talk. Should I do more of that? Do I just chatter on to fill the quiet for my own good? Does it help her?