That's Alice's cue to get up - considering she's doing so, moving over to help setting the table, especially when her mother is using that tone of all tones. She's grabbing the plates from a cupboard, holding them in her arms, but then turns towards Crowley for a moment.

"Mom.. It's okay. You know we love you, right?"

She figures she can easily use that 'we', considering there's not a doubt about whether her parents love each other. It's entirely obvious.