There are loads of shacks in Calangute, that sell summer type clothing, trouble is they are very similar to the clothes that the hippies wore, very bohemien, also they dont seem to make the clothes very large so if your wife is above 12/14 size she may have a problem. She can get them made up for her of course.

OK thanks.

Are there any shopping centres nearby that might have department stores?

I havent seen any department stores that sell western clothes, (only Mumbai) the department stores concentrate on selling sari's, and the indian suits. It is only around the tourist areas that you will find any of them selling western clothes, unless it is Nike, or adidas.