I agree with what @MelanieyM said. How does the party fit into your story/plot? Some cliffhanger party ideas on the top of my head:
- Is it a transformation story (geek to hottie)? If she’s at a party maybe she spilt punch all over the popular girl’s dress?
- Is it a romance story? Maybe because the lights are so dark she accidentally mistakes her boyfriend for the school bad boy and kisses him?