Ok, little bigger spoilers than usual. Do you really want to know? Scroll below:
Jen and Liam are silhouetted against the curtained door. Jen says: “She’s never going to find out”.
Naomi hears everything, she throws open the door. Shocked by the sight of Naomi, Jen scrambles: ” Naomi hi! Look, I don’t know what you think you heard but ..” Naomi, with a horrible realization replies ” It was you” “.
Jen is speechless, there’s nothing she can do. She looks at her sister’s cold face and leaves. As she goes, she glares at Liam. Liam grins at her .. victorious.
The whole scene ( how Naomi finds Liam & Jen ) was previously planned by Ivy, Liam and Teddy.
Source: 90210 Spoilers Guide