mrsfuzzy - Thank you :) Just seen your follow up - that seems a sad situation for your friend to be in and a very frustrating situation for you :(
I think deep down some people do have a preference. My husband for example really liked the idea of having a son. So when we went for our 20 week scan, I chose to find out the gender to ensure we both got used to the idea before the baby arrived.
His 'disappointment' lasted all of maybe .. 5 minutes before he got used to the idea of daddy's little girl :) His heart melts at all the lovely girls clothing we've bought for her.
If after all this it turns out to be a boy, we'll both probably need a bit of wine to get over all the pink clothes we now have before looking forward to life with our son!
Babies, life - everything is so unpredictable so it's not worth setting your heart on a particular gender, although deep down we all probably do.
Your friend does sound like she is struggling to let go of the idea of the 'girl baby' she was having and is almost grieving. Although I'm sure in time she will come to terms with it and learn to love the son she has, right now she needs support until she gains some perspective and her hormones sort themselves out.
You could encourage her to discuss her feelings with her midwife or health visitor and try to support her the best you can - listening to how she is feeling despite how unreasonable her views are. Her 'D'H really needs to step up as post natal depression or issues such as this are seriously and not something to be shrugged off. Your friend desperately needs some support and there is unlikely to be a 'quick' fix.
Good luck x