Miranda is Magenta's caring owner as well as a good friend of Steve. The character presumably met Steve after Blue and Magenta first met, considering the fact that the two dog-owners follow their dogs almost everywhere. She is one of the few live-action characters in the show.
She was originally portrayed by Shannon Walker Williams in the original and has apparently not met Joe because she made her final appearance before Steve left for college. She is played by Adriana Vasquez in the reboot.