My daughter accidentally left her iPad in the freezer overnight. What can I do now?

This Apple help page should provide some useful insight onto the temperature limits for both “in use” and storage. Whilst placing an iPad (or other electronic devices) into a freezer is not advised - if the iPad was turned-off and your freezer does not get colder than the minimum storage temperature - you might get away with it.

https://support.apple.com/en-gb/HT201678

Let it thaw out and then let it dry for several days. If you are sure that it has dried out, you can try powering up, but I wouldn’t have a whole lot of confidence that you will get positive results especially since it was getting hot before she put it in the freezer.

When you are able to do so, take it to an Apple Store and ask than what your options are.