I'm inclined to think early disseminated mostly because of the symptoms.
You are right - it's really impossible to know what prognosis for treatment will be but, her getting treated now/very soon can only improve the prognosis.
Is she detoxing yet? That can only help.
This site has some great suggestions:
www.tiredoflyme.com/detox-methods.htmlAnd, there are more in the "New to Lyme?" thread at the top of the forum.
Your niece as well as you and your family will be in my thoughts and prayers.