She saw a specific website's checkout screen.

Emma states "I walked in and saw your computer on. I figured you must be watching porn and went to clean yourself up after masturbating. So I wanted to see what you were looking at. Much to surprise". Emma continues "You were on some checkout screen on a website. You hadn't put any information in yet". "I quickly jotted done the website information so I could see what you were thinking about buying. When I heard the toilet flush. I ran back to get my purse hoping to get back out without you knowing I was there". You once again try to apologize to Emma but she cuts you off and, now Isabella really looks confused and very uncomfortable with where this conversation is going. "John" Emma starts to say. "I'm the one who should be apologizing".