K.J.
I think I cried as much as my son when starting to potty train him. But all of a sudden it just clicked. Once he understood what it meant to feel like he had to go to the bathroom, it got easier and he got more into trying. I would say definitely don't force her to go and I think we were trying to go every hour, not every 20 minutes. I started out playing games and telling/reading stories while he sat on the potty to try to go and sometimes even that lasted 10-20 minutes with nothing to show for it just to get into the routine.
I found something my son really liked and used it as incentive. He liked DVDs and trips to the park and ice-pops so if he cooperatied and went on the potty or had no accidents at day-care, when he got home he'd get to pick something as a treat. If he didn't cooperate, no reward. Eventually this worked and while the reward had to continue well after he was proficient at the potty, it eased my nerves, was easy to enforce and he seemed much happier. I suggested the reward to my friend and she started seeing progress after a week or two on her 3 year old.
I just kept telling myself that no one goes to kindergarden in diapers! Good luck and be patient.