It's difficult to know if your little girl has dementia, but I've attached a link to two checklists you can do. My little girl, Ashley, had very subtle changes that became more obvious when she was sixteen. The changes you described may be caused by other things. Ashley took Anipryl for her dementia. It helped with her anxiety and confusion. I hope your little girl feels better.
http://www.cdsindogs.com/PDF/CDSInDogs/ANIPRYL.pdf CDSInDogs