The only thing I can say is a lot of times babies know what they want. The pacifier is really more for them than we like to think it is, and if she doesn't want it, you will never be able to make her want it; the same as if you woudln't want something. And, generally, if they won't take something else in place of being fed, no matter how much they've just been fed or when/where it is, my experience with my son tells me that maybe they are just hungry little piggys... it's frustrating I know because they can't tell you anything...
If it is uncomfortable or inconvienient for you to breast feed in public or at times when you have to be out and baby is hungry, you should pump your milk and store it so the baby can eat. Even if you think your baby is eating a lot, ESPECIALLY if you are soley breastfeeding, I'll bet anything she's hungry and not just crying to cry, more so since she's only 2.5 months old. If you think she's full and continues to cry, and she is crying for more than three hours at a time and inconsolible, then it could be colic and you may just want to check with your doctor.
My son has always just used his pacifier when he wants it. He uses it now to chew on it for teething. We only give it to him at night or when we are going somewhere in the car because it keeps him occupied. He would flick it out of his mouth when he was even 3 weeks old, and sometimes he'll take it when he's upset, sometimes he won't...but that's okay because we've learned how to get him to stop crying...or, on the other end, how to just deal with it when he wants to cry. Sometimes, babies just need to cry, too...even if nothing is wrong...same as us...