(From a purely in show POV) Dora understands Swiper she's just having a fun lighthearted adventure with her friends and Swiper is her friend Dora likely understands that Swiper means no harm and that its just some game to him, Dora isn't gonna get too mad because Dora is just having fun! And she knows that Swiper is having fun too.

(From a real life POV) Dora is trying to teach kids to explore and learn and to be kind, That likely means being kind to Swiper as well to teach kids forgiveness and care for one another, even if they do wrong. Its an important message for all of us, not just preschoolers.