Hi Debbie
My Mum is a midwife and she says that if you have had it before you don't need to worry. But if you haven't had it you may be at risk, and remember that chicken pox is most infectious before the spots appear. Make sure you keep in touch to find out if your step-daughter starts showing spots, and if you start feeling ill go to the doctors as it can affect the baby.
Hope you stay well
Take care xxx