3 year old potty training

How do I get my 3 year old to potty train? She’s been left naked while we are at home for 6 months now. No accidents, goes pee and poop in the potty. But with underwear, she pees through. She won’t tell you when she needs to go, despite how we praise her when she goes and we take her every 15-30 minutes. She will say uh oh and clean it up but does it again. It’s becoming a hassle with her. Especially because when we go out we have to put a pull up on her and she will poop then tell you, won’t tell you before. Nothing makes her understand