1) Addlebrained 2) Airheaded 3) Bubbleheaded 4) Clueless 5) Easily addled 6) Easily confused 7) Eccentric to be kind 8) Empty-headed 9) Flibbertigibbety 10) Flighty and easily confused 11) Inanely silly 12) Lightheaded 13) Like a flibbertigibbet 14) Like a rattlebrain 15) Like an airhead 16) Like an eccentric uncle 1) Daft 2) Loopy 
Ditsy is slang for silly, eccentric, twee.
flighty and easily confused; mildly or harmlessly eccentric.