I am a nanny. I always try to keep in touch with my former charges. I ask about them once in a while and if we can we meet each other for coffee, lunch or birthdays.
I wish some of my former employers would send me school pix or holiday pics etc to see them grow. It doesn't happen much. They mean well but don't think about it.
Anyway it goes both ways to keep in touch and since you miss your nanny, just ask her over or send some texts once in a while, she will happily reply

Maybe she got busy with her new job.