E.S.
My daughter is 3 1/2 and I am in the same position. Frustrating, huh? I did get her to pee on the potty three times a couple weeks ago, but I decided to back of due to her hysterical screaming. She does not want to sit on a small potty or a big potty; she uses her underware like a diaper and has done some serious damage to the house with her accidents; she likes to look at the reward chart but doesn't care about the rewards; she has tried to convince me to stop going to the bathroom on the toilet and suggested I wear diapers too. She is stubborn and high strung so nothing other parents suggest works. I called her pediatrician today. She told me to stop training for 6-8 weeks and then have her pick out her underware and tell her it is her responsbility to sit on the potty when she has to go. When she goes, she gets a wrapped present. I don't know. I'll try it. It's still a variation of what I have been doing. She is in the biggest size of Easy-ups, so unless she plans on not growing, she is going to have to use the potty.
In regard to your situation, my pediatrician would likely adivce you to either stop the potty traiing for 6-8 weeks or gradually introduce underware into her training. Maybe have her wear it for three or four hours in the day for a while and then put her in a diaper or Pull-up if she still hasn't gone so that doesn't develop a UTI. Keep extending the time in underware if she starts to use the potty on her own? If we push them too hard, the potty training can backfire.