My first two children were exclusively breastfed and were pretty rotten about taking a bottle (they never did, even breast milk). But I didn't really push it like I could have.
It wasn't until my third child was born and I didn't have nearly the milk supply that I had with the first two. As someone who had nursed before, I KNEW my baby wasn't getting enough milk. At 4 months old, she had only gained 3 pounds.
It took me 10 days to get her to take a bottle! I offered one to her every time she needed to eat. She cried hysterically and wouldn't even put her tongue around the nipple. I was so scared for her because I knew she was hungry. On the 10th consecutive day of trying,she was screaming and stopped for two seconds to calm down and she sucked the bottle nipple. When she found out that something was coming out of it, she never turned it away again.
Now, my baby was starving and was happy to have food, but many moms only breastfeed for a few months and then go right to formula. She can do it, you just have to try every single day over and over again.
I personally really liked breastfeeding my older children, but when I found the freedom of the bottle, it was absolute heaven! I had trouble nursing my fourth child as well and had to supplement very early on. Bottles are good friends.
Remember, do it every day over and over when you would normally feed her. You might want to give her a bottle once a day so she is used to it when she needs it. If you are trying to get her to eventually drink formula, you might want to mix it half and half in the future.
Good luck! This is a tough one, but consistency is the key.
A.