I'm worried I may have been wrong about my ability to handle fostering

Even if you give birth to the child you can still be consumed by fear and anxiety. You get 9 months to bond with your newborn before it shows up for the love at first sight moment so give yourself some time to bond with this child. Your feeling are normal and the best way to handle them is probably to stop feeling guilty for having them but remember feelings aren't always true. Just try to keep your focus on her and not your feelings. The fact that you care so much about getting it right makes me think you are going to be a great mom.