How can a person get bacterial vaginosis by being with the only sexual partner ever? Considering she doesn't douche either.

Bacterial vaginosis. Bacterial vaginosis is the most common vaginal infection. It is an overgrowth of normal vaginal bacteria, not a sexually transmitted infection. When it mixes with blood or semen the ph gets elevated releasing the fishy odor. It is easily fixed with antibiotics. She wil need to be tested for other infections but this is the most likely.