I vaugley recall hearing about liners made for disposables to aide in TT. Has anyone used them or know someone who has? What do you think?

DD is playing coy on TT. I know she knows what is happening because when we went away, she'd run to the bathroom and stand infront of the toilet when she needed to wee/poo. Now she just hides and tells me she isn't doing anything. If I sit her on the potty or toilet she doesn't do anything and waits for the nappy... any ideas? I was thinking of these liners or using a pair of undies under the nappy? I've tried pull ups but she either doesn't notice she's wet or ignores it...

TIA

MG