How was she dressed? means, 1/ 'What was she wearing?' or, 2/ 'In what manner did someone dress her?' depending on context.
How did she dress? means, 3/ 'How did she go about dressing herself? or, if you add '...for the party' for example, it means, 4/ 'What did she wear for the party?' depending on context. Examples 1/ and 3/ are most likely.