Have a look here . I think (if you scroll down to Is it Infectious?) it can cause chickenpox in those who have not previously had it, through direct contact, but is not itself contagious. However a phone call to her GP/Midwife should clarify it.
If she's had chickenpox in the past, then she should be OK. You can't catch shingles from shingles, although people who haven't had chickenpox can catch CP from shingles.
My DS1 was 18 months when he had shingles and I was 7 months pregnant. Obviously couldn't avoid being in contact, but GP confirmed that I was OK as I had had CP. Baby was born at 42 weeks with no problems.
Thank you everyone. I have looked at the link and yes nailpolish have told her to ring her gp/mw. Looking at the link and knowing a firend who had chickenpox three times and shingles once I think she should not go even if it says it is not catching. It does say that shingles in pregnancy is serious and can damage the baby. Why take any risk is what I would say.