This page is for Sierra's relationships with others.
Jacob and Sierra are like siblings. The two have been friends since age 1.
- "The three of us instantly became best friends."
Mallory did not like Sierra, but in Jacob and the Bully, they became friends.
- "Mallory? Why would Mallory call you? She hates you."
Sierra and Patriot do not get along. In Patriot Returns, he said that Jacob and Sierra driving engines is disgraceful, which made her, Jacob, Duck and Percy cross.
In Patriot Returns, Douglas says Sierra is one of the best engine drivers on Sodor, to which Percy, Gordon, Duck, Donald and Diesel agree.