Re: how to switch from potty to toilet
The easiest way to get her to switch would be to get one of those seats that goes on top of your normal toilet seat and show her she can't fall in.. let her sit there when brushing her teeth or something and show her it is safe and the transition will happen..
As for how long you should continue with diapers a night.. that depends on the child. I would wait until she goes at least a week with waking up with a dry diaper before you even consider taking it off. Other wise you are just going to make things a lot harder on yourself.
Good luck I know what it is like having pushy daycare...