OK I got a few suggestions.
1. Have someone come to your house and pretend to be the "fairy god bottle mother" (you get the idea) anyway Have the fairy god bottle mother bring a gift with him/her in exchange for all the bottles she may have the gift. have the fairy god mother ask for the little girl and give her a big fantasy story about how she really needs her special bottles.

2. Have someone come to your house with a new born baby and ask for the little girl and have a big story made up about there are no more bottles. she has the last bottles in the world and her baby needs bottles.

3. DRASTIC MEASURES. Have all the bottles with you at a park or somewhere. Make sure she knows ALL the bottles are with you guys and then have someone come along and take them. "OMG we've been robbed of all the bottles. That man/woman just mugged all my bottles" ya know BIG SHOW. lol

I dont know just ideas. Maybe it'll help. I have 3 kids I know they like to thro fits when they cant have things. they dont last long because i dont give in. My famous sayin is. "ask again so I can say no" and i explain there waisting there time and energy cause the answer is and will stay the same. Think about this. If you could have a temper tantrum for anything in the world wouldnt you. I mean come on I think id have atleast a few a day. lol anyway best wishes take care.

--- Edited by stephaniedonithan at 2008-08-14 17:16:16 ---

I am not sure if I agree with telling children fibs. However, I do not have a problem bribing them. Have you tried making a reward chart so she can earn a prize? Maybe for every sippy cup she chooses over a bottle she can put a star on the chart. I would make it really easy at first. Maybe five stars the first day, 7 the second, and so forth. What about using peer pressure? It was a great help in potty training by 2 1/2 year old son by having play dates with other children close to his age who were potty trained. Maybe having your daughter spend time with another 3.5 year old (who has a really cool cup) and let her watch her friend drink from the sippy cup. Also, My 14 month old will lose interest before finishing his bottle when I switch the type of bottle he is drinking from or the temperature of the liquid.