S.P.
Insist on it.
Use a sticker chart.
Set a date when there will be no more diapers and stick to it.
Also, make her help you clean up any "accidents".
She is way old enough to be potty-trained.
It should have started to interfere with her life already....
I gave a star for every time they peed in the potty, and a sticker of their choice for every BM.
Sticker for being dry through the night and so on...
It would be ok to give a special "privilege" after a preset number of successes.
In other words, she could have a treat after a week of success for example.
New, pretty panties could be an incentive.
You could give her a pair each day that she has no "accidents".
I would stick around home for a week while you concentrate on this training.
Good luck.