It definitely changes from child to child. Your baby could take to the bottle and be perfectly content or she could completely reject the bottle regardless or when you introduce it or how you go about it. If you introduce the bottle too early, however, you do run the risk of nipple confusion and rejection because it is far easier for a baby to get milk from a bottle. They are very quick to get lazy.
My favourite resource for breastfeeding and all related booby matters is www.kellymom.com . Have a good look through it and try to take things a day at a time. All the best