Hey Lisa,
I haven't been there, so my methods are far from proven. However, if I were in your shoes I would try offering more "table food" soft fruits, veggies, plus whatever else she will eat. I don't know how often she's nursing, but if you chose to simply not let her nurse except at naptimes and bedtimes. Then offering the sippy, w/o the stopper if needed, at mealtimes and snack times.
Basically if she's eating food she'll be less hungry, and you can spread out the times you breastfeed. If she gets thirsty enough she will drink out of a cup. Just take it slowly and see what happens. I do suggest however that you don't even bother with the bottle, otherwise you'll need to wean her off that too. She's old enough to use a cup.
Hope this helps.