My son was a preemie and went home on a bottle of pumped milk. This continued until he was about 3 months - it's exhausting to pump, bottle feed, clean bottles, clean pump parts, etc. It's hard! I know what you are going through. What finally worked with him was to give him about an ounce from the bottle so he wouldn't be so hungry and then switch him to the breast. If you can start this on a weekend when your husband is there, you could start pumping on one side while she is drinking her ounce, then put her on that breast, so it is ready to go. While I know that this sounds like more trouble, you should only have to do it for a couple of days - hopefully she will realize how much better the milk is straight from the source!
I just finished nursing my third in four years, and have finally realized that each one is different. This last one would NOT nurse in public, with a blanket, etc and I am too modest to expose myself at the chickfila, so she had bottles of pumped milk or (gasp!) formula. She continued to nurse great until a year - I was lucky that she would take both. Guess what? She is the healthiest one of the bunch. The only one of the three that had exclusive breastmilk for the first year (the first one) has the worst allergies and more colds than the others. What I'm saying is, while I totally believe that breast is best - don't let the extremists make you feel guilty for using formula if nothing works to get this baby back to nursing. With two, you can't be tied down to your pump forever, and eventually you won't produce as much as she eats. You'll miss out on so much fun with your kids if you spend it feeling guilty. Good luck - I wish you the best!