This seems like a case of a little friendly competition between siblings. Alice and Trish are pushing each other to do their best, but they're making sure the rivalry stays friendly. Most importantly, they're putting their friendship and relationship as sisters first. Instead of working against each other to hog the glory, they're helping each another become better players.

Alice doesn't mind that her younger sib is better on the court; she's just a casual player, but Trish has a chance to be truly great. Alice probably senses this, and she's keeping a fun rivalry going so that Trish won't get lazy and miss her chance at b-ball fame. This is a case of a confident older sister helping a younger sib gain some confidence too.

If the two girls ever start getting into fights about who plays better or start showboating on the court rather than helping their teams, then they might be in trouble. For now, the friendly rivalry is actually doing them some good.