The New Adventures of Lassie - Season 1 Episode 19
Thin Ice

Humphreys niece, Samantha, brings a group of girls up from the city for her birthday party, she and Zoe dont get along. When Samanthas choice of skating ponds puts her whole group in danger, Zoe intercedes, saving Samantha and finding a true ally - which is a good thing, because its going to take both of them together with Lassie to save Harveys life.