Erica felt stupid.
Somehow (and she's still not sure how exactly, but she suspects that it happened sometime while she was staring down the front of her best friend's shirt), Callie had managed to talk her into continuing their little charade- the one where they were pretending to be a couple, a very touchy/feely lesbian couple- just to fuck with Mark Sloan's poor, pea sized brain. And as much as she loves torturing the manwhore of Seattle Grace, she's beginning to think that the real person who's being tortured is her.
Why you ask? Because Erica didn't just want to pretend to be Callie's girlfriend, she wanted to be Callie's girlfriend.
So as Callie giggled and flashed her what she imagined (hoped) were her bedroom eyes, one palm running up the length of Erica's thigh under a table at Joe's, it was only the sight of Mark Sloan hovering nearby that stopped Erica from falling into their game- from letting herself believe, for just a second, that it was real.
And that is why Erica felt stupid. Because even though she knew it would end in disaster and only leave her with a broken heart, a little part inside of her still hoped Callie would wake up one day and see just how amazing they could be.
End.