Potty training a 3 year old girl?

When my daughter was 2, she would refuse to even sit on the potty or the real toilet. By 2 1/2 i got her to finally sit, but she won't pee. She is now 2 & 9 months (she will be 3 in August) and there are times where she will sit there for 30-45 minutes, and will NOT pee. She gets the concept, and knows exactly what she should do, but when she feels the urge to pee, she freaks out, gets up and begs for a diaper. I wont give her one and she holds it in until she gets one. Eventually i give up and give her one. Times when she has underwear on, she pees in them and cries nonstop. I have tried stickers, juice, cookies, candy, presents, everything!! and the funny thing is when people come over the house, first thing she says to them is I WENT PEE PEE IN THE TOILET!! lol. IM A BIG GIRL. She always tells me she wants to go in the toilet, but when it comes down to doing it, she backs out. lol... any advise? has anyone bought potty training books? Im about to give up here.