First off, why do you want to quit breast feeding so soon, especially since you breast fed your son for so long successfully? I'm not trying to guilt you, I'm just curious why.
To help your daughter take the bottle, I read that whoever is feeding the baby should hold her upright and facing away from them. Give the baby pumped breast milk, and don't try to feed her the bottle yourself. She may not take the bottle right away because she's used to the breast. Basically, babies have to learn to suck from the breast, while they have to learn to stop the flow of a bottle's nipple, which is how they get nipple confusion. Make sure the nipples you purchase are slow flow. You could also try to leave a shirt you've worn for the other person to put over their shoulder for a comforting smell to the baby.