If you are enthusiastic about having her there, have a carer, & take time to prepare her....then it's an excellent chance that everything will be great. If you're not sure, or would rather not...she will pick up on those feelings too. If you arrange a babysitter at your or their house, & feel really secure about that, then she will probably feel very happy with it too.
I think this is so true Castle. If a woman/family takes birthing in its stride so will the child. This is one of the big keys to this. You are absolutely correct. Renee if you are not comfy then your child probably won't be. However, maybe after hearing some differing opinions (and the glorious diversity on Belly Belly gives us that) you may either be certain of not wanting yoru child there or you may be thinking it may be an option.
As Castle says, if you haven't got a designated carer, unless you are happy for your husband to focus on your child and not on you in the labour than you would need another person on board.

To digress slightly. After our son was born Ruby came home from preschool a few weeks later to announce that one of her little friends had a new sister. She said, "gee mum it was so wierd he wasn't even there to see him born". Now, in sharing this it is to illlustrate to my daughter the whole process was normal. It was normal to give birth, to poo while I did it, to holler, to cry, to laugh, to do all of the things that labouring women do. It was also normal to my daughter to be a part of it. For my daughter (because she was born into a home that birth, birthing, boobies etc were so openly and often discussed and seen) it was abnormal for her little friend not to be present at his siblings birth.

So, it is about different families also. My MIL and older SIL were absolutely horrified at our birth choices - they are very medicalised so some of my choices are difficult for them to get their heads around. However, many of my friends hold similar views so we had huge support.
Again, I have been at many births where children are present. They will watch in awe, go to sleep, eat an apple, laugh, breastfeed... They are just so earthed and normal birthing is so grounded that with the right preparation they almost always take it in their stride. However, if a parent were nervous or unsure as Castle says this will be reflected back onto the child.

With reference to what Fiona Jill says about a child being present at birth helping them to adjust to the new baby. I think that this most certainly has an impact. We haven'thad any issues with sibling rivalry (when a new baby is born) - and many parents report similar. My daughter now almost 12(eek!) has such a confidence in how women's bodies work. She isn't afraid to talk of her own body and knows just how much work goes into producing a baby. I think these are all good things.