There is no special female form for "brewer." Here is a definition of the term fromwww.cogsci.princeton.edu/cgi-bin/webwn
brewer - someone who brews beer or ale from malt and hops and water
The term "brewer" is gender-neutral. There is another term, "brewmaster," which, according to the Random House Dictionary of the English Language
(1977) has no feminine form.
In general, the -ess ending for female members of an occupation (as in actress, poetess, sculptress, stewardess) has been dropped. The American Heritage Book of English Usage: A Practical and Authoritative Guide to Contemporary English
"For occupational titles, the use of -ess is usually considered inappropriate and has been almost completely replaced by newly formed gender-neutral compounds or by the -er/-or forms."
"Brewer," however, has never had a feminine form.