In a statement, her Mum, Tina Coates, appealed for her daughter to return home.
She said: "A week since you went to the fair to hang out with your friends. Then didn't come home, what happened at the fair?
"Please message if you have any information about this, it would at least help to understand why she went away."
Ms Coates added: "We know you had difficulties with school, we know certain people liked making your life a misery in our town, that your hard shell was simply a way of protecting yourself. We know hour once happy little girl has changed in the last year and you were struggling."
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Ms Coates described how her daughter's disappearance had taken a toll on her. She said: "The pain and worry was horrendous a week ago and it's gradually becoming more and more worrying.
"Someone knows where you are, we just want you safe."
It has been confirmed that Katelan left Todmorden bus station in West Yorkshire at 6.05pm on Friday evening and took a bus to Burnley, Lancashire.
She was reportedly seen arriving at Burnley bus station at 6.53pm and has not been seen since. Police believe that Katelan may still be in the area.
Katelan is described as a white female who is around 5ft 5 with long brown hair. She was last seen wearing an orange vest top, black leggings, and a black coat.
A spokesperson for West Yorkshire Police said: "Officers and Katelan's family are growing increasingly concerned for her welfare and want to make sure she is OK.
"Anyone who believes they may have seen Katelan, may know of her current whereabouts or has information on where she travelled to after leaving Burnley bus station is asked to contact police without delay."