How to potty train girls?

My daughter is 3.5 years old and refuses to potty train; if you ask her if she has to pee, she says no. And then, 1 minute later, she pees her pants. If you ask her where she is supposed to pee, she will tell you she is supposed to use the toilet, but she won’t? I don’t put her in a diaper anymore; I’m using training underwear (thicker than regular underwear). Any tips are welcome!