E.H.
LOL !! Sorry i do not mean to laugh but i went through the same thing and thought i was gonna pull all my hair out!!!! I really understand and sympathise with you. I changed my sons routine and he use to be up til 3 am. He is 5 now and in school. Believe me it was not an easy task. My son has a tv in his room, and has had it since birth. We now lay him down at 8 p.m. and he gets one movie. Then the tv goes off !!! The next moring i proceeded to get him up at 7 a.m. That is plenty of time to sleep !! By the next night he was so darn tired he could barely stay awake til 8. I know it is gonna be rough but if you truely want to change her sleeping habits you have to bite the bullet. And not to pass judgement or anything but do you know for sure the sitter is only letting her sleep for an half hour???? Try no naps. Alot of sitters let children sleep rather than deal with cranky kids. They just do not want to mess with them.
I don't know it is just my opinion, but i hope it at least helps you find a way.