No more suggestions coming in, so I'll move on to 'dippy'. This is actually similar to 'dotty' but used more for a young woman. And yes, sexism is alive and well and thriving in the world of everyday English.
Whereas a dotty old lady is dotty because she's getting a bit senile, a dippy young woman is just, well... dippy. Forgetful, disorganised, scatterbrained.
Neither term is pejorative, by the way. Both character traits can be seen as endearing. You might speak affectionately of your dotty grandma or dippy sister.
'Fruity' doesn't quite fit into this set. The nearest term is if you describe someone as a 'fruitcake', which means they're crazy.