The Fox was a minor character during the film. It is worth noting that the totem pole had a fox on it, and Balto’s mother (Anui) mentioned Balto should get ready to meet “The fox, the cunning trickster” (among other spirit animals seen on the Totem pole).
When Balto followed the raven to the fox, he found her caught in a snare - after he initially thought the raven was talking to him and followed Fox's voice. The fox remained dignified/confident, and she didn’t act at all anxious about being trapped.
The Fox agrees to take Balto to Aleu (who she mentioned seeing). She then takes Balto by surprise and pushes him from the log, into the strong flowing river below them. At first, it seems she’s just being cruel. But ultimately, the fox did lead Balto to Aleu in doing so. Balto caught Aleu’s scent once he made it back to land.
Anui is a spirit guide, and could take the form of other animals (she changed into the bear, the 3 wolverines and likely the raven). So, it could be up for debate as to whether or not the fox was only an apparition who Anui posed as (meaning the vixen may or may not also be Anui. Aleu's spirit guide, Muru the mouse, was a separate spirit. Although unlike Fox and the others, he isn't on the totem)
That theory seems likely, as Anui seemingly caused all the apparitions of all the other animals on the totem pole – apart from the wolf, who she herself(and Aleu "The one who is wolf, but doesn't know it yet") is.
“And I thought you were a hunter. But unlike you, I am not disappointed” – The fox
“So let the current take you!” - Fox
Appearance: The fox is shorter than Balto + most dogs. But bigger than Dixie. She is wearing very distinctive purple eye shadow, she also has green eyes, totally black ears, black feet, white tail tip, white nuzzle/neck/underbelly and a very rich ginger-red coat.
Seen in - Balto 2 Wolf Quest
Voice Actor- Mary Kay Burgman