I recently lost a son at 22 weeks and I would say give her some space, but keep in touch. I felt like sometimes I didn't have the energy or the will to call someone or see people, but I really did appreciate people calling or sending an e-mail or a card. You don't have to say much--just say you are sorry, and then just be open to hearing whatever she feels like telling you. Also, be open to talking about completely unrelated stuff--I know sometimes I really like hearing about something else--so I am not sad all the damn time!
It means a lot to have people recognize what happened. There is not much else people can do. People who haven't called or even acknowledged it--it hurts a lot.
I personally have not felt any pain or jealousy around other people's babies or pregnancies. I know some people do. You can't pretend that you don't have a baby, so don't try. Just make yourself available and she will be back in touch, I am pretty sure.