It's not an easy one. I wonder if your DD is imagining a sister who will be able to do "girly" things with her from day one? Perhaps reminding her that the baby will be a baby, and not able to play with her for a while anyway, might help? That he will just sleep and eat for the first few months etc. By the time the baby is old enough for gender to matter, your DD will love him and be used to him, so she won't worry about his gender. Best of luck hun.