It seems like a huge change to constantly being with someone to being "locked in a box" from the babies perspective. She may feel like she is being punished or rejected in some way. So what ever you do will have to be gradual.
Have you tried putting her crib in your room? If you have her crib (or even a pack n play) right next to your bed then she can see you, smell you, and hear you and she isn't alone.
If she is held a lot during the day or has constant attnetion from the nanny have the nanny start trying to gradually reduce the constant attention. She could get your daughter interested in a toy and then sit back out of the way for a few minutes. Always there for your daughter to see and hear but not constantly focused on your daughter.
It is important for children to become independant and have time on their own even at a very young age. I used to sit my daughter in a bouncy seat when she was 4 months old, I'd sit right next to her but I would be reading a book or magazine. So I was right there so she didn't feel alone but because she saw me looking away from her she started looking away too. Children need attention, but not constant undivided attention.