He didn't ask for her. Lexie has been... hopelessly in love with George for a while now and he's been nothing but a jerk to her recently. I mean she's the reason why he passed his exam! Without Lexie, George would've repeated his year as an intern. She even decorated his locker as a way of celebrating this huge achievement and he didn't even had the decency to ask to have her assigned to him!
That's why she's been most of the night at Joe's Bar all by herself, denying everyone who asks to sit with her or buy her a drink. That's until she notices you walking in; a weight lifting off her shoulders as you shoot her that characteristic smile. When you asked to sit next to her; she simply nodded, looking away from you for a second before circling the edge of the shot glass with the pad of her index finger.
"I'm pathetic, yeah, i know..." Lexie breaks the silence with some whispered words, her voice lightly shaking thanks to both the emotions she was experiencing and the alcohol in her system.