While Jesus was talking about sowing and reaping with the disciples, the Samaritan woman herself told the other Samaritans about Jesus. And sure enough, a lot of Samaritans got to learn about Jesus and even came to him. They even wanted Jesus to stay, and because of Jesus's presence, even more Samaritans accepted Jesus as Lord and Savior. Now the Samaritans believed, not just because of the woman's words, but also because they have "heard for [themselves]" (4:42). Even today, people often accept Jesus because of a PERSONAL experience with knowing Jesus.
At the end, not only did Jesus impact the Samaritan woman, but the impact was so big that the other Samaritans were also impacted. The power of sharing Jesus (even just a referral or recommendation) creates a ripple effect.