In 6.03 After Life, we see that Buffy has photos of all the Scoobies on her wall except Giles. The photos include images of Buffy and Willow; Anya and Xander; Anya …

In 6.13 Dead Things, Buffy says of her bedroom,

“I think the New Kids On The Block posters are starting to date me.”

She’s referring to the American boy band, who …

At 13:47 in 7.09 Never Leave Me, you can hear Buffy close her bedroom door, but when the camera later shows it, it’s still open.

When the camera pans past Buffy’s bedroom before the funeral in 5.17 Forever, you can see that there’s no ceiling in her room.