how old is she? how dare they not let her use the toilet? you need to find out if that is the case or not, or whether your dd is using that as an excuse for wetting herself... but if she is generally dry why would she?
could you take some unpaid parental leave and enjoy the summer together?
i don't think they should have changed keyworker when they knew she was leaving - why disrupt her last few weeks. and clearly it has caused problems for your dd with the pant wetting. i would def speak to the manager
I would speak to the Manager and ask why they have changed her key worker for the last few works that your DD is there. Explain as you have done in your post, i.e. accidents everyday and repeat to the manager what your dd said, i.e. "I asked her if she'd been asking to use toilet and she says "I ask * (keyworker) but she says no".
Her care should not have altered because she is leaving. I would be very honest with the manager and ask her what she intends to do to improve the situation. She may not be aware of what is going on! Good luck