Toilet training tips

My daughter is ready to toilet train. We have been doing nappy free time in the afternoons for a good couple months now, getting her used to the potty and she happily tells me when she needs to wee or poo, or Now she more often just takes herself to the potty, sits down and does her business. When she has her nappy off and the potty out and easily accessible she will go on the potty probably 9 times out of 10 (every now and then if she's really engrossed in what she's doing she'll have an accident).

Now, I feel she is ready to go a step further and start wearing those training undies that are thick in the crotch area so the wee doesn't immediately run out. She is able to pull them down no worries, but when she has them on she will just wee in them and not bother with the potty. But she wants me to change them immediately after she has an accident.

Does anybody have some tips on how I can help her to tell me she needs to go BEFORE? So far I have just been repeating myself after each accident that she needs to tell me before she does a wee or poo so we can go to the potty, but she's not getting it... should I let her sit in the wet undies for a while? Or just keep reminding her and hope it clicks at some point? We're going through alotttt of undies haha.