Yes, they definitely have a secret. But this is something more important. Why would they hide that they are lesbians ? This makes them even hotter. There's something else. They're probably connected to Vinnie. And they may know about Chad's secret from Vinnie. I wouldn't be surprised if hacking a laptop is their doing.
Why is Josy hiding the fact she's bisexual? Why is Maya hiding her sexuality? We don't know the family situation of Sarah and Mel, they may be in a similar situation to Josy and Maya. Probably not as serious as Maya, but Josy has a loving father and is still unwilling to reveal that she's sexually attracted to girls to him. Just because the guys around college would think it's hot doesn't mean that it's a good thing for them to be out.
We know from ep 9 that Vinnie didn't need help with the laptop, he knew the combination of the safe himself before Rusty changed it, and going by what Rusty said the password hadn't been changed since Vinnie was a DIK. All he needed was to get in unnoticed which he could have done while everyone was distracted in the party room.
However given that Burke had access to the laptop too (probably remote) as he was able to get Jade's sextape from it, he's still my prime suspect.