A.P.
Have you tried the Madela bottles with slow-flow nipples? Or just slow flow nipples in general. They have a differnt shape than normal nipples and the milk actually comes out the top front of the nipple instead of the end of the nipple. These came with my Madela electric pump, but you can order them separately online. My daughter would only use these specific nipples. I even tried other slow flow nipples that look similiar with no success.
The other suggestion about expressed breast-milk was good. When I went back to work and didn't have enough time to pump enough breastmilk, I mixed expressed breast milk with formula one to one.
Good-luck! Have patience.