You need to look up the definition of sexist...
A pattern of a certain gender picking a profession is not sexist. Sexist would be if I only bought dogs from male breeders or female breeders based on the fact that they are that particular gender.
If you knew anything about the dog world, and read less internet articles, you'd realize that its dominated by women. Women outnumber men at least 10 to 1 at shows/trials/ect. So its only natural that most breeders would be women.