In a lesbian relationship, it is possible to pass on herpes even while taking medication. While antiviral medications can reduce the risk of transmitting herpes during sexual activity, they do not guarantee complete protection. It's important for both partners to communicate openly about their STD status and take necessary precautions such as using condoms or dental dams consistently to lower the risk of transmission. Consulting with healthcare professionals for personalized advice and regular testing are essential steps in managing and preventing sexually transmitted infections like herpes.