P.M.
Well, you've discovered the main drawback in linking desired behavior to a reward or bribe system, and a reason many parents will not use such systems. Your daughter's real reward will eventually be that she'll have greater control over her life, but there's very little you can tell her about that before she experiences it.
Nevertheless, your attitude toward your daughter's stubbornness and tantrums is almost certainly part of the problem. If you've worked on this for so many months that you are both frustrated about it, then your daughter will never experience the joy of self-control and gaining a new skill. When she complies, YOU will win, but SHE WILL LOSE. So what you have set up here is a power struggle. Imagine how unhappy that prospect must feel to your daughter.
Some children are not ready to train until 3 or even older. Your urgency about potty-training could be making it impossible for her to be emotionally ready. I hope you'll back off and give her some freedom to decide. If you search this site for other potty-training questions, you'll see many responses from moms who were surprised and delighted that their kids were suddenly ready to try the potty once they let up on all pressure.