This is not my opinion, but after reading this blog entry on Tumbler I am pretty sure the Pacifica like Dipper. Here are some of the theories that I read.
Why deos Pacifica like Dipper? Pacifica has picked on Stan and Mabel, but not Dipper. When Mabel saw Waddles, Pacifica joked that Waddles was “Mabel’s real twin,” suggesting Mabel is a pig, but not Dipper. The pig episode came after Irrational Treasure, so she may have respected Dipper for defending his sister, being more serious, or for giving into his need for revenge.”