Do you think it's all subconscious on her part? When she stops him from going she can't bring herself to say she needs him or wants him, just that she's 'not ready for you not to be here'.There's the graveyard scene in Potential when she unconsciously indicates concern for his welfare in the graveyard then tries to talk herself out of an attraction. Then there's the scene in The Killer in Me where she doesn't notice he's on the floor in pain despite him calling her. This is followed by the scene in First Date when she goes to check on him before she checks on Xander (but is flustered by Wood's gaze) then there's the scene you describe when she doesn't care who knows. It shows the gradual change in her feelings for him.
Yet she can casually say to Willow 'Why do people still think I'm in love with Spike?' . . . when maybe it's the way she acts around him that makes people think she still loves him 😁