You might want to try different kinds of nipples. Also some of mine tended to like the rubber rather than the silicon kind. I had a child that refused to take a bottle when she was 4-5 months old...I would walk her up and down the hall while giving it to her, and that helped.

If your wife is still breastfeeding, you can put some expressed breast milk in the bottle (if you haven't tried this already) to get her used to the fact that food can come from other things besides mommy's breasts. She should be able to take formula eventually after that.

If all else fails, you can use a sippy cup with a soft spout, which some babies can handle even at that age.