Don't know what early start philosophy you followed, but the one I followed had me "playing" with the potty for an hour every morning, with the key thing being putting the poop in the potty. I put my daughter in trainers at 18 months, and now at 24, she is almost 100% trained (including nighttime, we are having an issue at the moment, where she will pee if she has her undies on but not her cloth diaper. who can understand the logic of a 2 year old!)... The one thing I learned, however, is to KEEP AT IT. Consistency is key. Either the pee goes in the potty or it doesn't. If it does, then keep saying "pee goes in the potty." Also, they always go two steps back before going forward.
In any case, I think the key is getting her to poop on the potty. Once my daughter started doing that, everything else clicked. At the suggestion of one of my books, I started watching her when she would go off to her corner. For the first few days, I just talked to her about what was going on, and when she had gas, we talked about that too. Mostly, I tried to get her to focus on feeling the pressure. We also read "everybody poops." This helped immensely in getting her to stop hiding behind a chair when she went. After a week, I then just took her to the potty. Mind you, every day for two months I had her watch me put her poop in the potty. This is essential, if you ask me.
I also didn't bribe.Once she went on the potty for few times, I put her on a potty schedule and that was that: first thing in the morning, after snack, before lunch, etc. Praise works much better than other things (though I did use stickers when she would put up a lot of resistance). The key is to tell, not ask so: do you want to use the potty before snack or after snack. Do you want to use mommy's potty or my potty. Do you want to walk to the bathroom or do you want me to carry you. Create a happy dance and when she puts pee in the potty, do it and dance around. Then call grandma, call dadda, call everyone and tell them what a big girl she was.
It sounds to me like your daughter understands but is having some performance anxiety (thus going in the diaper after being on the potty). To help her overcome it, don't make a big deal out of it. Just keep saying "pee goes in the potty." Do all changing in the bathroom, do everything in the bathroom --that's where pee and poop go, end of story. It also sounds to me like she is still trying to figure out "control" (I see potty training as three key stages: 1. understanding dry and wet, 2. control (being able to relax enough to go on the potty on demand, and 3. timing. I read somewhere that they have to have 10-15 hits (pee in the potty) before they get how the muscles work. They will then spend more time trying to figure it out (a day to weeks, depending on the child's age). Your job at this point is to get the timing, so she can get the control. Load her up with water and try to get a hit. Keep trying, only show positive emotion, and when she does it, throw her up in the air and tell everyone around you, and let them praise her too for being such a big girl.
My daughter wanted her "big girl" undies so badly (elmo) that it motivated her to put her poop in the potty --three months after peeing consistently. I told my daughter that if she put all her poop in the potty for a week, she could have elmo undies. For nap, I told her she had to go 5 days with no accidents, and then 5 days dry at night as well. It really motivated her.