I think 'flowery blouse' is fine. It's clear what this means - a feminine-style blouse made out of a flower-print fabric. 'Floral blouse' is OK, too.

Floral is better option as it implies the print on the blouse has flowers / parts of flowers (like petals & stems). Flowery blouse would mean blouse made of flowers (which I doubt is not normally used :) )