We just bit the bullet with Charlotte - she was similar, would go at kinder etc - and we just one day put her in knickers. Gt rid of the nappy all together. She was also taking her self at home though too when she was nude, even if she didn't do anything.

Worked out really well... And worth a try. TTing doesn't have to be some time consuming process, sometimes they will just TT.
Maybe try putting her in knickers for day care days and see how she goes.

GL