It is an intense contest between Alisha and Olivia as they both struggle to claim victory.  When Olivia needs to pee, however, she must choose between keeping her pants dry and triumphing over Alisha.

In this scene we find Olivia and Alisha playing a video game together, in the midst of an intense competition.  Suddenly, Olivia pauses the game and starts to walk away, stating that she needs to pee.  As she does so, Alisha resumes the game, forcing Olivia to turn away from the bathroom and race back to her controller to avoid losing the game.  It is clear that Alisha isn’t going to allow Olivia to take a break from the game.  Olivia’s only options are to allow Alisha to win, to try and hold her bladder while trying to beat Alisha, or give up on her bladder and just focus on winning.

Olivia isn’t about to give up and let Alisha win, and having to focus on holding her bladder proves to be too distracting. The only option left is just to pee in her pants, and that is what she does.  It ends up paying off for her, though, as she ends up winning the game.