Shingles Support Group
Herpes zoster, colloquially known as shingles, is the reactivation of varicella zoster virus, leading to a crop of painful blisters over the area of a dermatome. It occurs very rarely in children and adults, but its incidence is high in the elderly (over 60), as well as in any age group of immunocompromised patients.
My own opinion is that your sister, because she has chicken pox, could very possibly give it to her baby. You, on the other hand, with shingles, will not give it to the baby, because it is so much harder for you to transfer the virus.