Please stop torturing your self and your little angel! She loves the breast, and she should! she is a human baby and has no business drinking the cow's milk or formula (my husband says is is very similat to a cheap bad tasting protein shake)--would you have that as your main sourse of nutrition? I bet no!
In terms of milk production, it works on supply demand-babsis. The more she will nurse the more milk you will produce, and it is a proven fact, you WILL! Try to nurse her on demand, as often as possible ( even every 30 min if possible at times) for a few days-a week and you will drammatically increase you milk supply. There is no reason to introduce a bottle to a breast fed 8 MO. especiallyu at that age the do know what they want and what they dont-and she seems like a strong willed lady!
Do offer her watter in a sippy cup every day, but do not make a big deal out if it, Just let her hold it whenever she wants to and show how to use it.
My son never took a bottle. He is 18 months old now, still breastfeeding, eating healthy foods and drikning water from the cup. He has great immune system, no allergies and is a big strong boy - all thanks to breastfeeding.
If you do deside to stop at 12 mo., there is still no nessesity for her to drink milk form any mammal (if the eats nutritious diet). she can get all she needs form fruits, veggies, cheese, yogurt, meats and water-as a means of hydration. Cow milk is for baby cows anyways, and if your child still needs milk in her diet---it should be yours!
You did such a great job breastfeeding for so long! Do not quit now! this is the easiest time to breastfeed. Enjoy your baby and the closeness you have with her.
I would also get a doctor who would be more sensitive and child oriented and not push you to withhold breastfeeding form your baby! 24 hours ( even 8) can cause her serios emotional trauma, not talking about dehydration. she trusts you to respond to her and take care of her day and night. Please do not break that presious bond and trust that she will value for the rest of her life! Our children need to be loved and appretiated---not TRAINED TO FIT OUR LIFE MORE CONVENIENTLY. Your little angel is a humam being, and you are her whole world. Just love her, trust your body and your baby and everything will work out!
good luck!
P.S. come to a La Leche League meeting with your baby, talk to other moms and leaders. You will get wonderful help and support with whatever you deside to do. here is a link : http://www.lllflorida.com/web/LakeWorth.html