I agree with what Maya said.

Another thing that you may gently want to tell your friend is that once the baby is born she will likely want to spend all her time with it, but I understand that prior to the baby's birth she might not even be able to imagine this. I consider myself a "career woman" and was never very maternal. I planned to work right up until I went into labour and to go back to work within three weeks of DD being born (just take annual leave - no maternity leave). Well, once DD was born, all that went out the window - so chances are that your friend may feel completely differently after the birth.

If she does keep asking questions, talk to her about why she plans to do what she wants to do, in a non-judgmenal way and maybe direct her to some research - someone posted a good article on FB today about breastfeeding helping you to lose weight, so maybe find it and send it to her, etc.

Oh, and the best thing that you can do as a friend is to be there for her after the baby is born. Don't worry so much about what she says now, as chances are she will change her mind.