In the episode "When Doves Cry", they find out about Craig's father and that he beats him. But at the party where he got to see his sister Angela, Spike and Snake are together. Emma stares right at them as Snake says "Oh just watching you turn gray" But she doesn't find out they're together until the episode "Girls Just Wanna Have Fun". That doesn't make sense because the episodes are far away.
In the episode When Doves Cry, Spike and Snake are just friends. The show doesn't even introduce them as a couple until Girls Just Wanna Have Fun. By the way, When Doves Cry is the episode right before Girls Just Wanna Have Fun, so it was technically only a week. Check out Degrassi.tv.